Damaged denticles "may impact their ability to hunt or escape," Auerswald adds.
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Using a scanning electron microscope to get an up-close look at the sharkskin, the researchers observed that 25 percent of the skin's denticles were damaged by the corrosive waters — dulling the denticles' pointed edges and their usually sleek surfaces.
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These skin denticles decrease drag in the water and help sharks glide more quietly.
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They have "dermal denticles," ergonomic scales that help them glide through the water with greater ease and speed.
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In free-swimming sharks like the great white, denticles account for up to 12 percent of their swimming speed.
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Shark skin is made up of tiny V-shaped scales called dermal denticles, because they resemble teeth more than fish scales.
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It takes longer than nine weeks to form new denticles, so the study did not establish whether exposure to acidic seawater impacts their development.
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After nine weeks, the researchers scrutinized the sharks' denticles with a scanning electron microscope, which creates super-detailed images by bombarding a surface with electrons.
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They found that on average, a quarter of the denticles on the sharks in acidic water were damaged, compared to 9.2 percent on the controls.
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This damage to the shark's denticles, the small, toothy structures that make up shark skin, could make them more vulnerable to infection or injury and slow them down by increasing drag.
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And now, thanks to climate change, humans may be transforming the very water sharks swim into an existential threat: In findings published today in the journal Scientific Reports, researchers show that prolonged exposure to acidified water corrodes the scales, known as denticles, that make up a shark's skin.
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An extremely rare second species, Oncodella mostleri, is only known from Hungary. It had three to four smaller denticles between the first and second large denticles, as well as a short rear bar without denticles.
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This lack of denticles distinguishes it from all but two species of skates found in the western Atlantic. Larger individuals do have three rows of smaller denticles on the tail, and mature females also possess denticles on the head and shoulders, and along the dorsal midbelt of the disk and tail. Denticles are completely absent on small individuals.
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Ventral coloration is black. The tail has 18 laterally compressed spines, the dorsal surface is covered in denticles, while the ventral surface lacks denticles.
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The morphology of the chelicerae is similar across all ages, with the same arrangement and number of denticles, but there were also some noticeable differences. Particularly, the principal denticles grew in size relative to the intermediate denticles, being 1.5 times the size of the intermediate denticles in juveniles, but up to 3.5 times the size of the intermediate denticles in adults. Furthermore, the terminal denticle was far larger and more robust in adult specimens than in juveniles. Perhaps most extreme of all, the second intermediate denticle is not different in size from the other intermediate denticles in juveniles, but it is massively elongated in adults, where it is more than twice the length of any principal denticle.
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The clypeus is shallow and measures (when excluding the denticles). It is broad, and the distance between its lateral-most denticles is . It is also more concave-shaped than it is straight. The oral margin of the clypeus is lined with a row of 30 denticles, which are peg-shaped.
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They also have rounded apices. The row of clypeal margin denticles is composed of two short rows. Each row is composed of 15 denticles each. The mandibles are short and barely overlap medially.
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Their scales, called dermal denticles, and teeth are homologous organs.
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The dermal denticles are scattered irregularly over the body and vary greatly in size, measuring up to across. Each denticle is thorn-like in shape, with ridges radiating out from the central point over the base. As many as ten denticles may be fused together to form multi-pointed plates. The underside of the snout and the area around the mouth is densely covered by small denticles in sharks under long; these denticles become larger and sparser in larger sharks.
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Its cusp is large, longer than the base, with about 4 to 6 denticles on each side of the median denticle. The first lateral has a subquadrate body. Its cusp has very small denticles, at its proximal, more conspicuous ones at its distal margin. The second lateral has a similar body, with larger cusp and more numerous denticles at its distal margin.
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Retrieved November 28, 2008. Their bodies are covered with minute dermal denticles; also, several rows of denticles are located inside the buccopharyngeal cavity. The shape of these denticles in Platyrhina and the similar Platyrhinoidis distinguish them from all other guitarfish species. Large thorns occur around the eyes and on the shoulders, and are arranged in rows along the back and tail.
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The very thin tail measures 2.6-3.4 times as long as the body, and lacks fin folds. One or two stinging tail spines are placed on the upper surface of the tail, about one-third of a disc width back from the tail base. A wide band of flattened dermal denticles, composed of larger heart-shaped denticles and smaller variably-shaped interstitial denticles, runs along the dorsal surface of the disc from before the eyes to the tail. Small, sharp denticles are scattered over the snout and concentrated at the tip.
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Placoid scales as viewed through an electron microscope. Also called dermal denticles, these are structurally homologous with vertebrate teeth. Placoid (pointed, tooth-shaped) scales are found in the cartilaginous fishes: sharks, rays. They are also called dermal denticles.
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Hindeodus is characterized by a P element with a large cusp, denticles that increase in width anteriorly (toward the head) except for the anterior-most denticle and generally decrease in height anteriorly, except for the posterior-most three denticles (the ones furthest back) which are at equal heights. Their cusps are much higher than denticles, and they possess S elements with a short lateral processes that are slightly upturned laterally with denticles of variable size. Hindeodus is differentiated from other conodonts by having P elements with large fixed cusps located at the anterior end of the blade and usually grow primarily by adding new denticles only to the posterior end of the element. Other conodonts vary in growth pattern and location of their cusps.
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The second and fourth maxillary teeth are the largest; the latter being the largest tooth of all. Of the ten teeth of the lower jaw, the first two are rather straight with an oval cross-section and lack denticles. The third tooth has denticles at its base and a flatter top; the other seven are more recurved and flattened along their entire height; gradually the denticles reach the apex.
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The function of the hedgehog segment polarity gene has been studied in terms of its influence on the normally polarized distribution of larval cuticular denticles as well as features on adult appendages such as legs and antennae. Rather than the normal pattern of denticles, hedgehog mutant larvae tend to have "solid lawns" of denticles (Figure 1). The appearance of the stubby and "hairy" larvae inspired the name 'hedgehog'.
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Annulicorona is an extinct genus of cartilaginous fish from Upper Triassic epoch of the Triassic period. Its name comes from the Latin Annulis meaning ring and Corona meaning crown, referring to the ring around the base of the crown of dermal denticles. It is known from the isolated dermal denticles of a single species, A. pyramidalis. The name refers to the roughly pyramid-shaped crown of the referred dermal denticles.
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The premaxillary teeth are pointed and lack denticles. The first four have an oval cross- section; the fifth is more flattened near its apex. The second and fifth teeth are the largest. The maxillary teeth are flattened with denticles on their trailing edges.
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They bear three very small but distinct and nearly equal denticles. The lateral teeth of the radula have only two denticles. Verrill, A. E. 1882. Catalogue of marine Mollusca added to the fauna of the New England region, during the past ten years.
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It has two reduced denticles at base of the ventral side of its movable finger.
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Chondrichthyans have toothlike scales called dermal denticles or placoid scales. Denticles usually provide protection, and in most cases, streamlining. Mucous glands exist in some species, as well. It is assumed that their oral teeth evolved from dermal denticles that migrated into the mouth, but it could be the other way around, as the teleost bony fish Denticeps clupeoides has most of its head covered by dermal teeth (as does, probably, Atherion elymus, another bony fish).
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The teeth appear to be mostly orthodentine, but when viewed in cross- section, change abruptly to osteodentine. The enameloid is single-layered, overlaying the thick mantle of orthodentine. In addition to the dentition teeth, there are also a number of buccopharyngeal denticles lining the oropharynx. The denticles lining the top of the head and the top of the spine- brush complex are larger than the dentition teeth, and they appear as elongate monocuspid denticles.
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In the taxonomy of trichodinids, the exact number, shape and arrangement of the cytoskeletal denticles is critical for determining taxonomic relationships. These characters are usually revealed by silver nitrate staining of microscope slides, which stains the cell cytoplasm black and leaves the denticles white.
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The origin of the genus is poorly understood. The common type species, Oncodella paucidentata, had a rod-like lower bar hosting a row of three to five denticles (tooth-like spines). The denticles were elongated, thin, and widely-spaced. They tilted backwards, especially towards the back of the platform.
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The edges of the teeth in the front of the jaw likely were not serrated, or at least only at the crown tips. This is usually the case in eusauropods. Teeth further back in the dentary are nearly all damaged, but a not erupted tooth has large denticles similar to basal sauropodomorphs. This pattern of teeth without denticles in front, and teeth with denticles in the back of the lower jaw is also seen in juveniles of Mussaurus and Melanorosaurus.
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The dorsal side of the head has its own collection of denticles which point posteriorly. The presence of these large denticles has led to theories that the spine-brush complex in combination with the denticles on the head was used to scare away predators by simulating the mouth of a larger fish. The complex has been affirmed only in males, and only in those males that have reached sexual maturity. Whether the complex was present in females of the species is still unknown.
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The flank dermal denticles contain a central cusp next to two lateral cusps and a second middle cusp above the primary cusp.Azevedo, Jose, Fernando Sousa, and Joao Brium. "Dermal denticles and morphometrics of the sailfin roughshark Oxynotus paradoxus (elasmobranchii, oxynotidae), with comments on its geographic Distribution." Cybium 27 (2003): 117-122. .
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P2–M2 have two widely separated roots, accessory denticles on the anterior and posterior cutting edges, and anastomosing striae on the enamel. P1 is caniniform with a single root. P2–4 have laterally compressed crowns and accessory denticles on the anterior and posterior cutting edges. P4 is the largest lower tooth.
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Along with the posterior serrations, there are 15 or 18 denticles per near the center of the teeth., although the anterior serrations have 17 to 20 denticles per . Given the dimensions of the preserved maxilla, Perle and colleagues suggested that Achillobator had a relatively large skull competing to those of carnosaurs.
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Membrane is black with a white spot. Hind femora along the lower surface have a row of straight, thin denticles.
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The rhachidian tooth (R) has a rounded body, with crooked hooks at the angles of the very concave posterior margin, and is thickened by a plate of a triangular shape, with concave sides. The cusp is considerably narrower than the body, which is large in front. It has a sharp point and a few small denticles on each side; the body of the first lateral tooth is larger, subquadrate, with a sharply pointed cusp and a few smaller denticles The second one has a similar, but more elongated shape and a sharper cusp, also with a few smaller denticles. The third lateral is long and slender, strongly hooked, with denticles at the base of the cusp, and resembles more the uncini.
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The pelvic fins are roughly triangular, and the tail is whip-like and measures twice as long as the disk is wide. One or more stinging spines are positioned between one-sixth and one- fifth of the way along the tail, and a narrow ventral fin fold originates closely behind the spine insertion. The skin is mostly smooth, except for a patch of small, flat dermal denticles at the center of the back. Some rays may lack denticles altogether, while others may have a 2-4 slightly larger denticles along the midline.
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Sebecus likely consumed food in a manner more similar to theropod dinosaurs than living crocodilians. In particular, the teeth of tyrannosaurids bear the closest resemblance to those of Sebecus. Both animals have serrated teeth with rounded projections called denticles, and sharp clefts between the denticles called diaphyses. These diaphyses compress meat fibers between the serrations and rip them apart.
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The aperture is whitish, elongate-ovate, with the outer lip showing many black denticles. The operculum is dark brown, thick and small.
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The crown tapers towards its tip. The edges have no denticles. The enamel shows the little wrinkles to which the specific name refers.
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The denticles were large, their number ranging from six to eight on the front part of the tooth, and five to seven behind.
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The tail is about 3.5 times as long as the disc and bears two stinging spines on top; behind the spines the tail becomes slender and whip-like, without any fin folds. Two recorded individuals had tail spines long with 70 and 89 serrations respectively. A band of skin running along the back from between the eyes to the tail base is roughened by small, flattened heart-shaped dermal denticles interspersed with small conical denticles. There are more denticles on the tail behind the spines, and small individuals also have a pearl spine in the center of the disc.
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There is a single serrated stinging spine on top of the tail; the fin folds are absent. The entire upper surface of the disc is densely covered by small dermal denticles that are heart or oval-shaped around the "shoulders" and become tiny and granular towards the disc margins; there are also around 5 relatively large denticles at the center of the disc. The tail is roughened by denticles above and below, with the largest positioned in a midline row before the spine. The dorsal coloration is a uniform light brown to gray-brown, darkening to blackish past the tail spine.
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The upper canine is a little larger than the upper incisors, and, like them, directed slightly buccally and mesially. P1, only preserved in a single specimen, is the only single-rooted upper premolar. Apparently, P1 is conical, smaller than the remaining premolars and lacks accessory denticles. P2 is the largest upper tooth and the first in the upper row with large accessory denticles.
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P. schroederi has typical denticles of the dorsal surface that are usually slender and leaf like, they bear a very long slender point directed up and back with two accessory points on either side. The dorsal dermal denticles of P. nudipinnis are thickened and broader rather than longer. They are about diamond-shaped, and paved.Ebert, David A., and Gregor M. Cailliet.
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The peristome is white with dark brown denticles on the outer lip and a brownish to reddish hue on the edge of columellar callus.
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Large yellowish blotches usually appear on the surface of the pectoral fins. The dorsal surface of the disc has uniformly dense coverage of dermal denticles.
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The specific name is derived from the Latin denticulata (covered with small denticles, pointed) as suggested by the laterally dentate gnathos diagnostic for this species.
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The dermal denticles of a alt=The dermal denticles of a lemon shark Unlike bony fish, sharks have a complex dermal corset made of flexible collagenous fibers and arranged as a helical network surrounding their body. This works as an outer skeleton, providing attachment for their swimming muscles and thus saving energy. Their dermal teeth give them hydrodynamic advantages as they reduce turbulence when swimming.
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Another unique feature of Ymeria is the presence of a large patch of tiny tooth-like denticles on the prearticular bone, which lies directly under the inner main tooth row. This patch of denticles is unknown in Ichthyostega or any of its relatives. All of Ymeria's teeth (on both the top and bottom jaws) were sharp but conical, in contrast to the recurved teeth of Ichthyostega.
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Placoid scales as viewed through an electron microscope. Also called dermal denticles, these are structurally homologous with vertebrate teeth. Shark skin is covered with placoid scales, or dermal denticles; leather made with these scales still attached is referred to as Shagreen. However, Ehrenreich had to find a way to remove these scales from the hides in order for his product to reach a wider market.
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The maxillae contained replacement teeth that had rugose enamel, similar to Camarasaurus, but lacked the small denticles (serrations) along the edges. Since the maxilla was wider than that of Camarasaurus, Brachiosaurus would have had larger teeth. The replacement teeth in the premaxilla had crinkled enamel, and the most complete of these teeth did not have denticles. It was somewhat spatulate (spoon-shaped), and had a longitudinal ridge.
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Neosauropods lack denticles on the majority of their teeth. In some species, including Camarasaurus and Brachiosaurus, they are retained on the most posterior teeth, but most advanced forms have lost them entirely. Certain members of the subgroup Titanosauria have ridges along their posterior teeth, but these are not large enough to be considered denticles of a form similar to those found in more basal sauropods.
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Reports of it from the Sea of Okhotsk may represent a different species. Its species name, spinosissima, comes from the Latin spinosus meaning "thorny", referring to its covering of dermal denticles. The flattened pectoral fin disc of the Pacific white skate is slightly wider than long, with broadly rounded tips. The disc is covered with numerous small denticles above and below, giving it a shagreen-like texture.
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The transverse sulci number about 10 on penultimate, 24 on the body whorl, including the base. The umbilicus is rather narrow, nearly cylindrical, encircled by a carina, above which a more prominent spiral rib revolves, which ends at the columella in three denticles. The very oblique aperture is circular. The columella is produced above in a lobe partly surrounding the umbilicus, below terminating in three denticles.
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The caudal fin is asymmetrical, with a long upper lobe and a well-developed lower lobe; the trailing margins of both lobes are convex. The skin is covered by tiny, non- overlapping dermal denticles. Unlike other Squalus species, adults have a mix of one-cusped and three-cusped denticles. This species is dark brown above, darkening towards the apexes of the dorsal fins, and pale below.
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In the Early Cretaceous Echinodon, there may have been two upper caniniforms, which were on the maxilla rather than the premaxilla, and Fruitadens from the Late Jurassic may have had two lower caniniforms on each dentary. Evolution of key masticatory specialisations in heterodontosaurids, according to Sereno, 2012 Like the characteristic tusks, the cheek teeth of derived heterodontosaurids were also unique among early ornithischians. Small ridges, or denticles, lined the edges of ornithischian cheek teeth in order to crop vegetation. These denticles extend only a third of the way down the tooth crown from the tip in all heterodontosaurids; in other ornithischians, the denticles extend further down towards the root.
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Based on Z. tonsora, queens are similar in appearance to Gerontoformica based on the mandibular structure; these mandibles have two teeth, one of which is apical (situated closer to the apex) and the other is subapical (below the apex tooth). Other similar body structures include the large ocelli, short scapes, 12 antennomeres (antenna segments), small eyes, and a clypeal margin that has a row of peg-like denticles (small bumps on a tooth). Queens can be distinguished from Gerontoformica by their flattened, broad heads. They have a broad, concave clypeal margin with a high number of denticles and two short vertical rows of denticles.
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The tooth sockets are rectangular in upper view. The jaw carries at least ten teeth. These are relatively slender, but the front teeth have a D-shaped cross section with the convexity facing outward; the rear teeth are dagger-shaped and more flattened. The cutting edges are convex and show up to thirteen denticles per five millimetres at the crown base, and up to eight denticles near the apex.
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Pristomyrmex tsujii workers are polished red, stoutly built and often foveolate. The propodeum is either armed with small denticles or entirely unarmed. The lack of strong propodeal spines separates workers, ergatoid queens and alate queens of Pristomyrmex tsujii from those of the sympatric Pristomyrmex mandibularis. The same character is used to diagnose the males, but the spines are reduced to denticles in Pristomyrmex mandibularis and entirely absent in Pristomyrmex tsujii.
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The sides are convex and small, yet protruding eyes are present. The posterior corners are round and the base of the ants' mandibles are concealed by the large expansion of the gena (area below the compound eyes, the insect equivalent to human cheeks). The clypeus is shallow and transverse, and 48 denticles that decrease in length can be seen on the clypeal margin. The denticles are peg-shaped with rounded apices.
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The basis is calcareous, thin, and does not form interdigitations with the wall plates. Soft parts are not specifically diagnostic, except the labrum has no denticles or bristles.
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Newborns and small juveniles have large, solid dark spots and few denticles. The leopard whipray is caught by fisheries in many parts of its range, primarily for meat.
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Propodeum armed with pair of small but distinct acute denticles to entirely unarmed. Propodeal lobes triangular, obtusely rounded. Fore tibial spur pectinate. Middle and hind tibiae lacking spurs.
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Bulletin of Marine Science 87.3 (2011): 501-12. Ingentaconnect. Web. 2 June 2013. The 3-point denticles distinguish P. schroederi very apparently from all other species of Pristiophorus.
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Analyzing the three components of the scale it can be concluded that the base of the denticle does not come into contact with any portion of the fluid flow. The crown and the neck of the denticles however play a key role and are responsible for creating the turbulent vortices and eddies found near the skin's surface. Due to the fact that denticles come in so many different shapes and sizes, it can be expected that not all shapes will produce the same type of turbulent flow. During a recent research experiment biomimetic samples of shark denticles with a crescent like microstructure and tested in a water tank using a traction table as a slide.
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The (serrations) were large and bulbous, diminishing slightly in size towards the tooth tips, with about 5–6 denticles per . The front (cutting edges) folded upwards to overlap the inner surface of the crowns on the third to eighteenth teeth, but such folds were absent on the second and probably first crowns. The denticles were roughly perpendicular with the tip of the tooth crowns but parallel to the crown height on the front side fold and triangular facet on the hind side. There was a series of accessory denticles (in addition to those on the carinae) that projected from the front surfaces of the carinal folds, which made the front edges of the crowns more broadly roughened.
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The columella has only faint indication of denticles. The siphonal canal is short. The color of the shell is white with brown bands in the sutures.E.A. Smith, 1884: 1884a.
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The teeth that are recovered are all labiolingually compressed with denticles along the edges, hence they are ziphodont, and the crown curves distally. A fossil tooth of an Iberosuchus.
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The lacrimal likely did not form part of the border of either the orbit or nares. The palatine bones of the roof of the mouth in the front part of the snout extensively contacted the maxillae. Some bones in the front part of the palate (likely the vomers) were also covered in small denticles. Denticles were also present in the back of the palate, likely on the pterygoids and rear parts of the palatine bones.
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The specialized pharyngeal denticles with brush-like branches of Branchiosauridae are indicative of gill clefts and suggest a filter-feeding mechanism focusing on plankton. In well preserved specimens of Branchiosaurus, six rows of tooth-bearing ossicles are present on each side of the hyobranchial skeleton in a 1-2-2-1 configuration. This is consistent with the denticles being attached to the epithelium surrounding four cartilaginous ceratobranchials bordering three external gill- slits.Milner, A.R. 1982.
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The outer side of the second metacarpal has but a shallow groove for the ligament that connects it to the third metacarpal. When the arm is seen in a flat position, of the second metacarpal the edge between the wrist joint and the upper shaft is straight in top view. The teeth have fifteen to twenty denticles per on the rear edges and twenty to twenty-seven denticles on the front edges.
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The body of the third lateral is elongate, with a moderate cusp and only a few denticles. The fourth has a very large cusp, with about 10 small denticles and a rhombic body. Moreover, I see a fifth lateral without cusp. Perhaps this tooth exists in many or in all the species, but it is so much covered by the other teeth in their normal position, that it may be easily overlooked.
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Radula of Hadroconus sibogae The rhachidian tooth (R) of the radula has a subquadrate body, with rounded posterior corners, enlarged sides and a short, reflected cusp, with a few denticles. The lateral (l) is subtriangular, with a short, reflected cusp, with small denticles at the distal margin. I can detect no more teeth, belonging with certainty to the median part. The uncini (U) are long, slender, with distinct smaller teeth near the top.
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This species can be distinguished from its two closest congeners, B. giddingsi and B. lutarius, by a combination of prominent comb-like dermal denticles along the upper caudal- fin margin, absence of oral papillae, uniform body coloration, and noticeable dark dusky snout; Bythaelurus giddingsi has oral papillae present and a variegated color pattern, while B. lutarius lacks a caudal crest of enlarged denticles and matures at a much smaller size than the new species.
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The mandibles have the typical shape seen in the genus, overlapping slightly when closed, and with apical and subapical teeth. The clypeus sports approximately 32 denticles, though the type description originally placed the denticles on the labrum. While the type description mentioned the lack of a sting, the 2016 review of the fossil suggested the sting may have been missing prior to entombment. The species name was derived from "Cretaceous", the age of the fossil.
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Pups have a double row of enlarged dermal denticles to help them exit the eggcase. After hatching, the pup is approximately 15 cm in length and is fully self- sufficient.
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The outer lip is incrassate with 8 denticles. The wide siphonal canal is short and straight. Smith E.A. 1884a. Diagnoses of new species of Pleurotomidae in the British Museum. Ann. Mag.
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He agreed with Benton that Rileya is dubious, but suggested that Palaeosauriscus may be valid, based on its now-destroyed tooth with a "subcircular cross-section and fine, obliquely inclined denticles".
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The spire is higher than in Citharomangelia richardi (Crosse, 1869). The fine spiral striae are distinct. The columella shows traces of transverse plicae. The outer lip is denticulate with 13 denticles.
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Behind the sting, there is a deep ventral groove and prominent lateral ridges running to the tip of the tail. The upper surface of the disc is densely covered by tiny heart-shaped dermal denticles in a wide central band from between the eyes to entirely cover the tail, with those at the center of the disc are slightly larger and spear-shaped. Newborns lack denticles; the denticles on the "shoulders" and head are the first to develop. This species is grayish brown above, with many small dark spots covering all or part of the disc and tail base; sometimes there are also subtle to prominent white spots, that may be arranged into rosettes surrounding the dark spots or into indistinct rings ("pseudo-ocelli").
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All five of these bones are covered with tiny tooth-like bumps known as denticles. Larger fangs, similar to the marginal teeth, were also present on some of these bones; the first and second coronoids each have two of these fangs at their front outer corner and the parasympheseal has a single large fang in the middle. Additional denticles may have been present on the dentary, which has a small number of small bumps on the outer surface of the parasymphyseal region. If these were true denticles, then this is a surprisingly "primitive" feature present in Andersonerpeton, as this feature is typically considered to have been lost very early in the evolution of tetrapods (specifically, after the evolution of Elginerpeton).
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Tooth of cf. R. isosceles with close up of denticles The holotype specimen of Richardoestesia gilmorei (NMC 343) consists of the pair of lower jaws found in the upper Judith River Group, dating from the Campanian age, about 75 million years ago. The jaws are slender and rather long, 193 millimeter, but the teeth are small and very finely serrated with five to six denticles per millimeter. The serration density is a distinctive trait of the species.
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The supraoccipital bone, which forms the top portion of the back of the skull, is flat and nearly vertical, as is the case in Probactrosaurus and other hadrosauroids. Dentary of Eolambia As with the premaxilla, the predentary of Eolambia bore denticles. There is a prominent dorsomedial process, a tab-like structure also seen in Probactrosaurus and other hadrosauriforms. Several additional tab-like denticles were present on either side of the dorsomedial process, which are likewise present in Probactrosaurus.
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Hypothetical life restoration The tooth is two millimeters tall and very recurved, with a strongly convex front edge and a nearly vertical back edge. The tooth is stout, with a maximum fore-aft length of 1.9 millimeters. Both edges are serrated, showing low rectangular denticles (individual serrations). The twelve denticles on the rear edge are much higher than the fourteen on the front edge, which cover only the nearly horizontal upper part of the front edge.
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The tooth base, though very wide, is constricted. The base is asymmetrical, with the right side in front view protruding much further than the left side; because it is not known whether it is a left or right tooth, it cannot be established what is the inner and what the outer side. The denticles are separated by "blood grooves", and "blood pits" are also present. The back denticles point obliquely upwards but have no hooked upper corners.
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No anal fin, grooved dorsal fin spines, teeth with narrow cusps and cusplets in upper and lower jaws, uniform dark coloration Short abdomen and short caudal peduncle, close-set denticles on body.
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The disc has dermal denticles but generally lacks thorns (some specimens have small thorns just anterior to the axil of the pectoral fins). The tail has 25 small, oval-based midrow thorns.
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The aperture is narrowly oblique. The outer lip is thickened and furnished with four strong denticles. The columellar teeth are more obscure and feeble. The sinus goes deep into the outer lip.
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Logania is a genus of jawless fish which lived during the Silurian and Early Devonian period. Like other thelodonts, the body was covered in denticles, which in Logania were interlocking and stud-like.
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Usually a single serrated, stinging spine is placed on the dorsal surface, relatively close to the tail base. Adults have a broad band of small, flattened dermal denticles running centrally from before the eyes, over the back, onto the tail. At the center of the disc, there is an enlarged, round "pearl" denticle trailed by 2-3 smaller thorns along the midline; there are no enlarged denticles on the base of the tail. Newborns have large, well-spaced dark spots covering the disc.
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The caudal fin is short, with a small lower lobe and a ventral notch near the tip of the upper lobe. The body and fins are densely covered by tiny, overlapping dermal denticles. In addition, there are enlarged denticles that form prominent saw-like crests on both the dorsal and the ventral edges of the caudal fin. The dorsal coloration consists of dark saddles along the back and tail, which are wider in F. boardmani and thinner in F. striatus.
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The whip-like tail is no longer than twice the disc width and bears 1 (rarely 2) stinging spines on the upper surface. Both dorsal and ventral fin folds are found behind the spine, with the ventral fold 2.5-3 times longer than the upper fold. A single row of thorn-like dermal denticles runs along the midline of the back and tail; with the largest found at the base of the tail. The number of enlarged midline denticles increases with age.
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The full complement of denticles is restored by synthesis of new denticles from the outer edge of the cell, working inwards. Trichodinids are typically found on the gills, skin and fins of fishes, though some species parasitise the urogenital system. A range of invertebrates is also host to trichodinid infections, including the surfaces of copepods and the mantle cavity of molluscs. Transmission occurs by direct contact of infected and uninfected hosts, and also by active swimming of trichodinids from one host to another.
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The teeth are oval-shaped with a moderately pinched upper end and have coarse denticles, these denticles have three diminutive pointed structures. It appears to be that the dentary teeth were more flattened with a pinched lower end as indicated by nine isolated teeth. In all teeth, a ridge-like structure is located at the center. An isolated and partial right jugal is represented by AMNH FARB 30657, which has lost most of the anterior area in the rostral joint.
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The parabasisphenoid (base of the braincase, towards the rear of the palate) is triangular and also covered with denticles. The mandibles are not well-preserved in any specimen, but seemingly lacked any unusual features.
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The maxillary and dentary teeth are elongated, only recurving near the top, with perpendicular denticles on both edges. Their bases are circular in cross- section; the top of the tooth crown is more flattened.
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The ovate aperture is narrow and measures about 10/23 the total length. The columella is callous. The outer lip is incrassate with 11 short denticles. The wide siphonal canal is very short and straight.
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Because of the slow replacement rate, this grinding produced extreme tooth wear that commonly obliterated most of the denticles in older teeth, although the increased height of the crowns gave each tooth a long life.
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The caudal peduncle is long and thin, particularly in younger sharks. The caudal fin makes up one-fourth to one-fifth of the total length and has a weak lower lobe and a ventral notch near the tip of the upper lobe. The thick skin is covered by well-calcified dermal denticles, except around the gill slits. Enlarged, spike-like denticles are found on the upper surface of the pectoral fins and along the dorsal midline from the snout to the second dorsal fin origin.
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There are also thorns on the dorsal surface of the disc and tail. The dorsal coloration consists of ochre vermiculations separating brownish-white oval or circular spots about the size of the eye, becoming more distinct towards the margin of the disc and on the pelvic fins. The denticles and tail spine are ochre-colored, and the underside is light tan with a dark border along the edge of the disc. The coloration, denticles and several proportional measurements distinguish the Tumbes round stingray from other Urobatis species.
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The pectoral fins are angular, twice as long as wide, and originate beneath the fourth gill slit. The caudal fin is low, with an indistinct lower lobe and a shallow ventral notch near the tip of the upper lobe. The skin is delicate and sparsely covered by thorn-like dermal denticles interspersed with narrower hair-like denticles that become more numerous on the back. The coloration is a plain brownish gray all over, sometimes lightening to almost white at the dorsal, pectoral, and pelvic fin margins.
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The height of the shells of the recent shell is 2.5-3.3 mm. The species differs from Pupilla muscorum by its smaller size, the strongly rounded and ribbed whorls and the lack of denticles and crest.
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It has a light colour in deeper waters, but becomes darker between tide marks. The foot is light yellow or light orange. The admedian teeth of the radula have denticles. The penis is flat and broad.
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Thick, globose shell, up to 5 cm, with low spire, large body whorl and flat base. Colour white with dark brown nodules. Dark violet, narrow aperture with conspicuous groups of denticles. Columella with three strong, plicate ridges.
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Placoid scales on a lemon shark (Negaprion brevirostris) Placoid scales are found on cartilaginous fish including sharks. These scales, also called denticles, are similar in structure to teeth, and have one median spine and two lateral spines.
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Although the skull in general possesses a combination of amniote and non-amniote features, the palate noticeably lacks amniote adaptations. Most of these missing adaptations relate to the pterygoid bones, which are elongated blade-like structures that lie along the middle of the palate. The palate lacks "labyrinthodont" features such as large fangs, and instead the pterygoids are completely covered with small tooth-like prickles known as denticles. This is unusually primitive compared to early amniotes, which typically have denticles concentrated in only a few parts of the pterygoids.
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At least two different tooth morphologies are observed among therizinosaurids; the first is represented by relatively homodont, oval to lanceolate-shaped teeth with moderate coarse denticles (serrations) on the crowns (upper exposed part). This type of dentition is better represented by the complete, three-dimensional holotype skull of Erlikosaurus which features the mentioned characters. Two isolated teeth are known from the therizinosaurids Nothronychus and they are lanceolate-shaped, symmetrical, have moderate denticles, and strongly resemble those of Erlikosaurus. Furthermore, they seem to derive from the dentary based on comparisons with Erlikosaurus.
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The preserved holotype dentary tip of Neimongosaurus preserves an erupted tooth that is lanceolate-shaped with small coarse serrations, falling within this type of dentition. Another type of dental morphology is the one seen on the highly specialized Segnosaurus. In this taxon, the teeth are very heterodont, leaf-shaped with relatively less denticles that are prominently developed being bigger than in the previous therizinosaurids. These denticles are composed of numerous folded carinae (cutting edges) with denticulated front edges, creating a roughened and shredding surface near the base of the tooth crowns.
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When intact, the tail measures 2.5-3 times as long as the disc is wide. There is a band of small, dense, heart-shaped dermal denticles extending from between the eyes to the tail, becoming larger in a midline row before and after the sting. In addition, 3-4 enlarged, spear-like thorns are present at the center of the disc, along with 1-3 preceding rows of smaller thorns that run to just behind the eyes. Minute denticles are also present on the remainder of the disc upper surface.
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The first dorsal fin is low with a minute leading spine; the second dorsal fin is twice as high as the first with a much larger spine. The caudal peduncle is short, leading to a long caudal fin with the upper lobe much larger than the lower. The dermal denticles of this shark are tiny and densely placed with no regular pattern; each denticle has a four-cornered base and rises to a narrow, slightly curved point. The denticles of females are firmly attached, while those of males are easily removed.
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The tail is whip-like and measures 1-1.5 times as long as the disc is wide. A long, serrated spine originates in the first third of the tail, and is followed by a low dorsal keel and a ventral fin fold. Young rays have smooth skin, while adults have a patch of small dermal denticles between and behind the eyes, and a row of thorns along the midline of the back. There are 1-6 tubercles in front of the tail spine, and numerous small denticles behind.
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Larger, heart-shaped denticles are scattered over the disc, especially around the "shoulders" and the middle of the back. Two pearl spines are present. There is a line of 40-41 flat tubercles running down the dorsal midline, from between the eyes to the tail spines; adult individuals also have two lines of spiny denticles running along the sides of the tail from the spine to the tip. The dorsal coloration is white to light gray, with brownish hexagonal blotches forming a reticulated pattern that fades towards the disc margin.
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There are pits at the intersections of the denticles, and the points of the denticles point towards the tip, or apex, of each tooth. The teeth show wear facets on their sides. Holtz (1998) also noted that characteristics used to support a predatory habit for Stenonychosaurus – the grasping hands, large brain and stereoscopic vision, are all characteristics shared with the herbivorous/omnivorous primates and omnivorous Procyon (raccoon). Age determination studies performed on the Two Medicine troodont using growth ring counts suggest that this dinosaur reached its adult size probably in 3–5 years.
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The outer lip is provided with 6-7 elongate denticles of which the third (from adapical side) is markedly larger. The parietal edge has a broad, thin and shiny callus, continued to form a broad shield also bordering the columella; provided with small blunt tubercles and molded over the varix of the preceding whorl but never bearing a distinct plait or denticle on the adapical side. The columellar edge forms a thick outgrowth which extends over the aperture, provided with denticles which increase in size towards the adapical side. The siphonal canal is short.
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The skin is thick and densely covered by small, overlapping, well-calcified dermal denticles; each denticle has a leaf- shaped crown with a horizontal ridge and three teeth on the posterior margin. There is a prominent, saw-like crest of enlarged denticles along the dorsal margin of the caudal fin. G. murinus and G. springeri also have a similar crest along the ventral margin of the caudal fin. Galeus species are typically grayish or brownish above and lighter below, and most have a pattern of darker saddles and/or blotches along the back and tail.
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The outer lip is thick, incurved, serrated on the edges at the termination of the transverse striae. The ovate aperture has no denticles. The siphonal canal is short and slightly recurved. The colour of the shell is white.
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Retrieved on December 9, 2008. The skin is entirely naked, without spines or denticles. The coloration is a deep chocolate brown. All Lasiognathus are small fishes; L. amphirhamphus is the largest known species at 15.7 cm standard length.
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Herbivores grind their molars together as they chew (masticate), and the ridges help to shred tough plant material. A material similar to dentin forms the hard material that makes up dermal denticles in sharks and other cartilaginous fish.
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Shell is cretaceous, white; consists of five convex whorls and a deflected ultimate whorl. The aperture is thickened, projecting internally in two subconcrescent denticles (described by Tryon as "tubercles"). The average diameter of the shell is 25 mm.
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Chrysocetus is similar to Zygorhiza except that it lacks the denticles on the cingula of the upper premolars characteristic of Zygorhiza. The premolars of Chrysocetus have smoother enamel than other dorudontines and are more gracile than those of Dorudon.
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Upper and lower palatal folds strong, the lower longer. Basal fold stout, in a subcolumellar position. Usually there are small suprapalatal and infrapalatal denticles. Peristome is thin, a little expanded, the outer margin biarcuate, with a median entering angle.
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The aperture is long and narrow. The outer lip shows a thick varix. The inner lip is smooth or with small denticles. The ten opisthocline axial ribs are more or les prominent but do not project above the suture.
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It lacks eyes. Its mandibles are rod-like, with anterior dentition. Its maxillae has 7 pairs of free denticles. It also counts with two peristomial segments without setae, its parapodia being uniramous and showing short dorsal and ventral cirri.
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The smooth lanternshark forms a species group with the blurred lanternshark (E. bigelowi); these two species are distinguished from other lantern sharks by their irregularly arranged, truncated (ending in a flat crown as though the tip were cut off) dermal denticles.
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Teeth and jaw of a female Leafscale gulper shark. The leafscale gulper shark has no anal fin, two dorsal fins with spines, the first dorsal being relatively low and long, large eyes, and rough leaf-like denticles. Its maximum length is .
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It contains 12 axial ribs on the penultimate whorl. The aperture is narrow and long. It measures about half of the total length of the shell. The outer lip shows 9 small denticles and is slightly sinuate at the top.
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Blythophryne is distinguished from other bufonid genera because of its small adult size. Osteology: Presence of six presacral vertebrae, absence of coccygeal expansions. General Anatomy: Have elongated pair of parotoid glands, expanded discs at digit tips, Phytotelmonous tadpoles lack oral denticles.
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Adults have a broad band of tiny, closely spaced granules extending from before the eyes, onto the tail. At the center of the disc, there is a midline row of up to 15 enlarged, heart-shaped denticles, with the two largest ones located one after the other between the "shoulders". There are no enlarged denticles on the base of the tail. When born, this species is grayish to brownish above with large black spots, a row of dark spots on either side of the tail until the sting, and beyond it alternating dark and light rings.
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The experiment showed that the surface with denticles experienced a 10% drag reduction overall versus the smooth sample. The reason for this drag reduction was due to the fact that the turbulent vortices became trapped between the denticles creating a ‘cushion like’ barrier against the laminar flow. This same type of experiment was performed by another research group which implemented more variation in their biomimetic sample. The second group arrived at the same conclusion as the first however because their experiment contained more variation within the samples they were able to achieve a high degree of experimental accuracy.
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The second dorsal fin also bears a spine in front and is over twice as large as the first in area, with the span between it and the first dorsal fin approximately equal to the distance between the snout tip and first gill slit. The anal fin is absent. The caudal fin is low and narrow, with an indistinct lower lobe and an upper lobe about as long as the head. The dermal denticles on the sides of the body are stout and thorn-shaped, widely spaced without any regular pattern; the snout is mostly covered by denticles.
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The Hortle's whipray (Himantura hortlei) is a little-known species of stingray in the family Dasyatidae, occurring in shallow estuaries and mud flats off southern New Guinea. This species, growing to across, has a heart-shaped pectoral fin disc with a long, pointed snout and minute eyes. It has a wide dorsal band of dermal denticles extending from in front of the eyes to the tail, as well as scattered sharp denticles on the snout. The underside of the disc is a distinctive bright yellow in color, sometimes with darker markings around the nostrils, mouth, and gill slits.
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The overall form of the tooth, its width and shape in cross-section and its curvature resemble those in the maxilla (upper jawbone) and mandible of the species Dromaeosaurus albertensis from North America. Blood grooves are indistinct or absent, also similar to Dromaeosaurus, and differing from members of the Velociraptorinae subfamily. Dromaeosauroides differs from Dromaeosaurus in that the cutting edge at the front side is further from the middle of the tooth. Although the tooth is larger and the denticles similar, each denticle was smaller than those of Dromaeosaurus, which had only 13–20 denticles per , instead of Dromaeosauroides' 30.
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In 2012, Buffetaut posited that this pattern would begin with large serrations in primitive Jurassic taxa like Ostafrikasaurus (from the Tithonian age), which resembled those of typical, similarly-sized theropods. These would then evolve into the fine, reduced, and more numerous serrations of Early Cretaceous baryonychines, like Baryonyx from the Barremian of Europe, and Suchomimus from the Aptian to Albian of West Africa. Baryonyx, for example, had seven denticles per mm (0.04 in) in comparison to Ostafrikasaurus's two to four. Finally, the denticles would disappear entirely in spinosaurines such as Spinosaurus from the Albian to Turonian of North Africa.
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There are 4-5 papillae (nipple-like structures) across the floor of the small mouth. The small teeth are arranged in 4-5 series in the upper jaw and 14-15 series in the lower jaw; in some individuals, the outermost teeth are stained orange-brown. The whip-like tail lacks fin folds and bears one or two serrated, stinging spines on the upper surface, which are seldom found intact. The dermal denticles are better-developed than those of H. signifer, with a central band of denticles covering the dorsal surface of the disc and tail base.
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The pelvic fins are short and can be rotated forwards; the males have short, stout claspers. The slender tail measures over twice the length of the disc and lacks fin folds. A single stinging spine is found on the upper surface of the tail near the base, but is frequently missing in adults. The upper surface of the disc and tail are covered by minute, blunt dermal denticles, with slightly larger plate-like denticles forming a distinct, broad band extending from before the eyes to the base of the tail; this denticle band is present at birth.
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There is no nictitating membrane and the cornea is continuous with the skin surrounding the eyes. The gill slits are on the ventral surface just behind the head and there are five in all species except the sixgill stingray (Hexatrygon bickelli). The front few vertebrae are fused into a synarcual and this either articulates with the bones of the well-developed pectoral girdle or is fused to them, the suprascapulae uniting above the vertebral column. Most species have enlarged, thorn-like dermal denticles on their skin, often with a row of large denticles along the spine.
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M.alfredi with cephalic fins rolled up (Yap, Micronesia) The two species of manta differ in color patterns, dermal denticles, and dentition. M. birostris has more angular shoulder markings, larger ventral dark spots on the abdominal region, charcoal-colored ventral outlines on the pectoral fins, and a dark colored mouth. The shoulder markings of M. alfredi are more rounded, while its ventral spots are located near the posterior end and between the gill slits, and the mouth is white or pale colored. The denticles have multiple cusps and overlap in M. birostris, while those of M. alfredi are evenly spaced and lack cusps.
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The length of the anal fin base exceeds the distance between the anal and pelvic fins, and is comparable to the distance between the dorsal fins. The caudal fin is short and low, with a small lower lobe and a ventral notch near the tip of the upper lobe. The body and fins are entirely covered by minute, overlapping dermal denticles; each has an ovoid crown with a horizontal ridge leading to a marginal cusp. There are distinctive crests of enlarged, spiny denticles along the anterior half of the caudal fin upper margin, and beneath the caudal peduncle.
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It lacks fin folds and usually bears a single serrated stinging spine. Adults have small, rounded dermal denticles covering the central dorsal surface of the disc, beginning in front of the eyes and extending to cover the entire tail; there are also small, sharp thorns on the midline, which become densest at the base of the tail. Juveniles are either smooth-skinned or have a sparser covering of flat, heart-shaped denticles. This species is uniform grayish to brownish pink above, becoming dark gray to black on the tail past the sting, and uniformly light below.
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The underworld windowskate has a heart-shaped disc, with denticles on the blunt snout, around the eyes, on the pectoral fins and down the sides of the long tail.Kells, Val., Carpenter, Kent. A Field Guide to Coastal Fishes From Maine to Texas. 2011.
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The denticle (tiny teeth) of radula have the formula ∞ 1, (1 + 1 + 1), 1 ∞. The central denticles are small and elongated. The lateral tooth is rather large, straight, without a cusp. The numerous lateral teeth are denticulate, and arranged in very oblique series.
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The whorls of this relatively high-spired shell are rather flat-sided and show a fine sculpture. Some of the denticles of the outer lip extend into the aperture. There is a number of variation in the spiral cords of the examined specimens.
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Many species have the ganglia in a compact space. The rachiglossate (rasp-like) radula, a layer of serially arranged teeth within the mouth, has only three denticles (small teeth) in each transverse row. The Neogastropoda have separate sexes. There are about 16,000 species.
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The periphery is roundly carinate. The convex base contains nine fine granulose cinguli with axially lirate interstices. The obliqua aperture is tetragonal. The outer lip is thick, with two rows of denticles, the outer corresponding to the cinguli, the inner about six in number.
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The vacuities widen and become broadly rounded near the level of the basal process. Small ossicles filling the interpterygoid vacuity indicate there was a plate of denticles in the vacuities. (cite Montanari). The vomerin tusks are larger and placed in a more lateral position.
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In the lower molars the accessory denticles on the mesial edges are replaced by a deep groove called the reentrant groove. The apical cusp is the primitive protoconid. M2 and M3 are morphologically very similar. M3 is sitting high on the ascending mandibular ramus.
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There are also 1-5 enlarged, oval denticles in a row between the "shoulders". This species is uniform grayish to light brown above, with the eyes and spiracles rimmed in white, and uniform white below. Females grow up to across, while males are smaller.
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They wedge a bivalve open using the edge of their shell, and insert their long proboscis to eat the flesh of their victim. They rasp at the flesh using their radula, a rough tongue-like organ that has thousands of tiny denticles (tooth-like protrusions).
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Trichodina is a genus of ciliate alveolates that is ectocommensal or parasitic on aquatic animals, particularly fish. They are characterised by the presence of a ring of interlocking cytoskeletal denticles, which provide support for the cell and allow for adhesion to surfaces including fish tissue.
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The front teeth are not serrated: those more to the rear only have denticles at the trailing edge. Five sacral vertebrae are present; the tail probably consisted of about thirty vertebrae. The pubic bone probably pointed obliquely to the front. The ischium is elongated.
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It possesses no eyes, its mandibles being L-shaped, counting with anterior serration. Its maxillae exhibits 7 free denticles. It also counts with two peristomial segments without setae. Its parapodia has dorsal ventral cirri, with simple supraacicular chaetae and compound subacicular chaetae with serrated blades.
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Between dentary, surangular and angular a rather tall triangular mandibular fenestra is present. The dentary bears twenty-one teeth, which are slightly larger than those of the upper jaws. All teeth of Jiangjunosaurus are symmetrical with a triangular profile. Front and rear edges have both seven denticles.
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Callus is rather blunt and only slightly curved. Parietal wall has two lamellae (the anterior lamella may be dissolved into small denticles). Lower parietal plica is free or connected to the anterior lamella. Palatal plicae are oblique, or depressed Z-shaped, usually in contact with each other.
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Restoration Young et al. (2012) identified seven autapomorphies of P. manselii that this species possesses to the exclusion of all other metriorhynchids. P. manselii have rectangular- shaped denticles in lingual view. Its tooth enamel ornamentation is largely inconspicuous, but there are apicobasally aligned ridges of low-relief.
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The skin is devoid of dermal denticles. The coloration is uniformly yellowish above, sometimes with an ill-defined brown stripe running down the back. The yellowback stingaree is likely ovoviviparous with low fecundity, as in other stingarees. Males mature at a length of 23 cm (9 in).
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The operculum is ovate, thin, corneous and spiral, with polar point well forward and approximating the columella. The jaw is thin and membranaceous. The radula is odontophore, with teeth are arranged in transverse rows, according to the formula 3 + 1 + 3. Formula for denticles of rhachidian: .
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The aperture is narrow. The outer lip is much thickened with large denticles on the inner surface, and the columella is toothed. Melvill J.C. & Standen R. (1896) Notes on a collection of shells from Lifu and Uvea, Loyalty Islands, formed by the Rev. James and Mrs.
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The large dermal denticles are overlapping and bear three to five horizontal ridges each. The coloration is a plain yellowish brown or gray above and lighter below, with more yellow on the fins. This species attains a maximum known length of , though it typically does not exceed .
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The anatomy of this species was firstly published under the synonym Australorbis nigricans in 1955. The body length varies from 56 mm to 64 mm. The radula has from 125 to 168 rows of denticles (tiny teeth). The number of lateral teeth varying from 28 to 36.
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The skin is soft and lacks dermal denticles. The Japanese sleeper ray is reddish to chocolate brown above and paler brown below; some individuals are plain, while others have dark or light spots over their dorsal (rarely also ventral) surfaces. The maximum known length of this species is .
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The orthocline axial ribs are crossed on each whorl by 7–8 strong spiral lirae forming small tubercles. The body whorl is slightly inflated and shows 9–14 spiral lirae. The outer lip shows 3–5 denticles..The white aperture is ovate. The peristome is simple and slightly incrassate.
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The outer lip shows 11 strong inner denticles. The anteriormost, weakest, delimit the siphonal canal and the posteriormost delimit the anal sinus. The siphonal canal is short, widely open and slightly curved. The ground colour of the shell is orange- tawny, with lighter cordlets and rare white tubercles.
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It is the largest nematode in birds, with females measuring 72 to 112 mm long. The body is semitransparent, creamy-white, and cylindrical. The anterior end is characterized by a prominent mouth, which is surrounded by three large, trilobed lips. The edges of the lips bear teeth- like denticles.
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The aperture is nearly horizontal, tetragonal. The superior lip is straightened, bearing a very large subbifid squarish tubercle in the middle. The place of the periphery is marked inside by an entering lamellar fold. The basal margin is curved, slightly expanded, bearing two or three fold-like denticles inside.
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Newborns are entirely smooth but develop denticles quickly after birth. Juveniles have four circular tubercles at the center of the disk, which often become indistinct in adults. The coloration is a uniform grayish brown to black above and mostly white below. The tail fold and tip are black.
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The sinus is ample and profound. The three denticles of the outer lip, those of the columella, and the sutural tooth are all tinged fulvous red.Melvill J.C. & Standen R. (1896) Notes on a collection of shells from Lifu and Uvea, Loyalty Islands, formed by the Rev. James and Mrs.
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The bases of the pelvic fins extend past the first dorsal fin base. The caudal fin is broadly triangular, with a gently convex trailing margin. The skin is entirely devoid of dermal denticles. This species is light tan above and lighter below, darkening slightly towards the disc margins.
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It can reach lengths of up to and can weigh up to . There have been unconfirmed reports of individuals reaching lengths of . A barndoor skate typically weighs . The tail is moderately short and does not have large, thorn-like structures called dermal denticles that are normally found on skates.
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Plicidentine was once considered to characterize "labyrinthodont" amphibians such as temnospondyls, but it is now known to occur in some extinct amniotes as well. The supratemporal bones at the rear of the skull roof formed small horns, and the palate (roof of the mouth) was covered in small cones known as denticles. Denticles reached almost as far back in the mouth as the large, robust quadrate bones which formed the upper part of the jaw joint. Preserved portions of the braincase were generally similar to those of other reptiles, with the exception of a large opening (likely for the hyomandibular branch of the facial nerve) at the front edge of the base of the braincase.
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Indication of three semilunar pockets along a shallow groove between the dentary and the prearticular shows that the lower jaw has three coronoids. It is unique in that it has a very large adductor fossa, a convex ventral flange, and a prearticular of minute denticles dorsally and undulating parallel ridges ventrally.
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The external mandibular fenestra is large. The dentary, lower jaw, teeth are quite pointed and have no front edge denticles; their rear edge is very straight. The holotype preserves a furcula and a basket of fifteen pairs of gastralia. The arms are weakly developed, with a slender humerus and ulna.
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The external shell surface is quite variable in color. It may be bright or dark red, orange or brown with a small white or yellowish transversal band on whorls and with small white patches on varices. The outer lip is ornamented with 8–10 white prominent denticles. The columella is reddish.
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Debase : To lower the silver/gold value of the coin by altering its purity, but with the same face value as the pure coin. This often happens during periods of high inflation. Denticles : Small toothlike projecting points on the inside edge of coins. Designer : Artist or creator of a coin's design.
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This genus includes two extant species of uncommon, little-known sharks. Both species are relatively large sharks, at in body length. They are characterized by a short nose and by rough, thorn-like dermal denticles scattered over its body, some of which may be fused together. They have no anal fin.
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Adult shell size of Homalocantha anatomica varies between 38 mm and 63 mm. These shells are solid, whitish in color, sometimes tinted with yellow or red and moderately light in weight, with five to six varices per whorl. Aperture is small and white or pink. Labial lip shows irregular denticles.
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Only three teeth are preserved on the dentary, one of which contacts a maxillary tooth's inner surface with its outer surface. The denticles on this tooth's outer surface perfectly match up with those of the inner surface of the maxillary tooth, forming a chisel contact surface for grinding or cutting food.
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M1–3 have accessory denticles on the posterior cutting edges. P2–3 are two-rooted. Outside the upper one-rooted teeth and inside the upper two-rooted teeth there are pits for reception of the lower teeth. Zygorhiza (and Dorudon) replaced their upper and lower deciduous first premolars with permanent teeth.
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The dental formula of the stenoglossan radula of Assiminea vulgaris is 1 + 1 + 1 + 1 + 1 + 1 + 1. The central tooth has five cusps, and three denticles on each side, below. The inner lateral tooth has six cusps and the outer lateral tooth five. The marginal teeth show 15 pectinate cusps.
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Trichodinids have a simple direct life cycle. That is, they have a single host and do not use alternation of generations or mass asexual replication off the host. They reproduce by binary fission, literally cell-splitting. This produces daughter cells with half the number of denticles of the parent cell.
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The results of principal component analysis performed on an outline analysis of some thelodont denticles. Outline analysis is another approach to analyzing shape. What distinguishes outline analysis is that coefficients of mathematical functions are fitted to points sampled along the outline. There are a number of ways of quantifying an outline.
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The dermal denticles are tiny, smooth, and non-overlapping. Adults are grayish to golden brown above and white below, with faint darker saddles and white patches on the dorsal fins. Juveniles have a striking pattern of large black markings on a white background. This species can grow up to long.
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The base of the body whorl contains a strong groove delimiting the outer part of the siphonal canal. The aperture is rounded. The outer lip is somewhat thickened externally although not forming a varix. Inside the outer lip there are numerous denticles elongated in the spiral direction and alternating stronger and weaker.
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The coarse grater is used to grate daikon and similar foodstuffs, whereas the fine graters are used for grating wasabi or ginger. The fine graters are also sometimes sold as a wooden board covered with shark skin, which has many tiny teeth (dermal denticles) and give it a feel similar to sandpaper.
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Out of both the low and high-profile samples tested, the low profile vortex generators outperformed the current smooth wing structures by 323%. This increase in performance is due to a separation bubble in the denticles wake and stream-wise vortices that replenish momentum lost in the boundary layer due to skin friction.
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The synapomorphies that define Pipoidea are the absence of mentomeckelian bones, absence of lateral alae of the parasphenoid, fusion of the frontoparietals into an azygous element, greatly enlarged otic capsules, and a tadpole with paired spiracles and which lacks beaks and denticles. Later genetic work has supported Pipoidea as a monophyletic group.
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The 7 axial ribs are high, strong and compressed and are narrower than the intervals, not becoming weak below suture. The ribs are crossed by fine, flattened striae. The inner lip is smooth or with small denticles or weak ridges. The ovate aperture is narrow and measures about half the total length.
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Under a microscope some of the very small spiral lirations are seen to be minutely granulated. The inner lip is smooth or with small denticles or weak ridges. The ovate aperture is narrow and measures about 5/11 the total length. The columella is straight and shows a 7-8 transverse folds.
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The arrowhead dogfish has an extremely long angular snout, no anal fin, small first dorsal and long rear dorsal spines, and pitchfork-shaped dermal denticles. The first dorsal fin is short and placed high on the back. This is the smallest of the genus Deania, with a maximum length of only 76 cm.
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Shells of Chicoreus capucinus can reach a size of . These large shells are heavy and solid, elaborately textured, uniformly dark brown, with six convex whorls. They are sculptured with prominent spiral cords, axial ribs and striae. The aperture is rounded or oviform, brown tinged and the inner labial edge show 14–17 denticles.
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The oblique aperture is tetragonal. The outer and basal lips are thickened and plicate within. The oblique columella is inserted nearly in the bottom of the broad umbilical excavation, its edge reflexed and bearing about 10 denticles, twisted near the insertion, terminating below in a simple tooth. The parietal tract is wrinkled.
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The upper surface of the tail bears a serrated stinging spine, which is preceded by a relatively large dorsal fin. The caudal fin is lance-like, short, and deep. The skin is devoid of dermal denticles. This species is yellowish to brownish above; many individuals are patterned with small pale spots and reticulations.
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Charlton Standard Catalogue of Canadian Coins 2006, p.89 A novel feature was an inscription of Morse code on the coin. This International Code message meant "We Win When We Work Willingly" and was placed along the rim on the reverse instead of denticles. The regular reverse and composition were resumed in 1946.
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The teeth of Crosbysaurus are triangular in outline with serrations on both edges. Almost all specimens have "compound denticles"; serrations with their own subdivisions. The serrations on the trailing (posterior/distal) edge of the tooth are always larger than the leading (anterior/mesial) edge. The teeth are small, approximately 3-5 millimeters tall.
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The width of the shell is 0.9-1.1 mm. The height of the shell is 1.6-2.2 mm. It is wider than the shell of Carychium tridentatum which it closely resembles. As in C. tridentatum shell is dull white and cylindrical and the mouth is oval with two denticles and a thickened lip.
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The teeth are mostly exposed when the mouth is closed. The tail is equal in length to the disk, with loose lateral folds of skin and two dorsal fins of equal size. The tips of the dorsal and caudal fins are angular. The skin is soft and loose, without denticles or thorns.
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The dorsofrontal side of the ants' head has fine, sparse setulae. A protruding gena can be seen, with a narrow but extended apex well past the clypeal denticles. The dorsoventral portion of the frons has shallow V-shaped grooves that extend over the antennae bases. There is no evidence of any frontal carinae.
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Apart from electric rays, which have a thick and flabby body, with soft, loose skin, chondrichthyans have tough skin covered with dermal teeth (again, Holocephali is an exception, as the teeth are lost in adults, only kept on the clasping organ seen on the caudal ventral surface of the male), also called placoid scales (or dermal denticles), making it feel like sandpaper. In most species, all dermal denticles are oriented in one direction, making the skin feel very smooth if rubbed in one direction and very rough if rubbed in the other. Originally, the pectoral and pelvic girdles, which do not contain any dermal elements, did not connect. In later forms, each pair of fins became ventrally connected in the middle when scapulocoracoid and puboischiadic bars evolved.
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All seven maxillary teeth are molariform, though they vary greatly in size; the first three and the last two are much smaller than the two middle ones, only about half the size overall. All the maxillary teeth have one deep root, oval in cross-section, and there is a slight constriction between this and the crown of the teeth, which are flattened obliquely to produce a spatulate shape. The outer surfaces of the maxillary teeth are smooth and bear a few grooves, whereas the inner surfaces are covered in denticles that grow smaller towards the tip of each tooth. The two large central molariform teeth have a second set of denticles around the base of the inner surface of each tooth.
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However, the upper and lower teeth are distinctly heterodont, and can be readily distinguished from each other. The upper teeth are relatively short and broad at their base, with 4–6 denticles on each surface, similar to ornithischians; the lower teeth are almost twice as tall and have twice as many denticles, more closely resembling the teeth of sauropodomorphs. The four premaxillary teeth are the longest teeth in the upper jaw, and are more recurved back in shape than the rest. Medial view of a right maxilla from A. madagaskarensis, showing the keel on its rear half The palate is unusually covered in numerous fully developed palatal teeth, with up to four sets on the pterygoid and additional rows on the palatine and vomers.
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The praemaxilla is short. There is a fenestra promaxillaris, a small opening in the front of the maxilla side, which is rare among troodontids. There are four premaxillary and about twenty- three maxillary teeth. The maxillary teeth have no serrations on their front edge; the denticles on the concavely curved rear edge are small.
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The outer and basal margin have short plicae in the interior. The concave columella is reflected over the umbilicus, with two denticles near its base, of which the basal one is the largest. The parietal wall has a layer of enamel, connecting the margins, slightly projected over the umbilicus. Its margin is a little thickened.
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The sole of the foot is without a defined median area. Two small labial tentacles are present. The color is reddish-brown, splashed with black, and darkest above. The mantle and sole are ashy-yellow. The radula is 12 mm long and 3 mm in width. It has 61 rows of denticles (tiny teeth).
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The rest are convex with a shallow suture. The 12 opisthocline, almost straight axial ribs (11 on the penultimate whorl) are rounded and are wider than the intervals, not becoming weak below suture. The ribs are crossed by fine, flattened threads. The inner lip is smooth or with two small denticles at each end.
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Pycnodontiform fishes lived mostly in shallow-water seas. They had special jaws with round and flattened teeth, well adapted to crush food items. One study links the dentine tubules in pycnodont teeth to comparable structures in the dermal denticles of early Paleozoic fish. Some species lived in rivers and possibly fed on molluscs and crustaceans.
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Dorudon atrox skeleton Basilosaurids ranged in size from . Like all archaeocetes, they lacked the telescoping skull of modern whales. Their dentition is easily distinguishable from that of other archaeocetes: they lack upper third molars and the upper molars lack protocones, trigon basins, and lingual third roots. The cheek teeth have well- developed accessory denticles.
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There is no evidence of a respiratory organ, though the bursa may have served this purpose. Schematic diagrams of Ottoia sclerite morphologies. Sclerites comprise a broad, flat basal pad and a thickened, usually triangular arch. Denticles arise from the lateral margins of the arch; distal extension of the arch gives rise to a prong.
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A phylogenetic study performed as part of the study split the family into two clades. One clade was a subfamily termed Rhinesuchinae. Rhinesuchinae contains Rhinesuchus and Rhineceps. This subfamily is mainly characterized by features of the palate, such as an anterior branch of the pterygoid lacking ridges and palatine bones covered in tiny denticles.
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The tail is somewhat flattened and measures 77-84% as long as the disc. There is a single dorsally placed, serrated stinging spine around halfway along the tail, and no dorsal fin or lateral skin folds. The tail terminates in a long, low, leaf-shaped caudal fin. The skin is entirely devoid of dermal denticles.
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They are long, slender and hooked, with apparently smooth cusps. The outer ones are shorter, broader, with a few denticles on each side near the top, visible if expanded. The number of uncini is not large, but Schepman could not ascertain the exact number.Schepman 1908-1913, The Prosobranchia of the Siboga Expedition; Leyden,E.
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The whorls are ventricose and ribbed longitudinally, crossed with a few conspicuous lirae. The outer lip is much thickened with large denticles on the inner surface, and the columella is toothed. Melvill J.C. & Standen R. (1896) Notes on a collection of shells from Lifu and Uvea, Loyalty Islands, formed by the Rev. James and Mrs.
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The skin of young sawfish is smooth, but on older individuals, it is sparsely covered in dermal denticles. The dorsal (upper) side of the fish is greyish and the ventral (lower) side and fins are a pale grey color. The rostrum is grey with white teeth and sometimes has a chocolate-brown base portion.
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2 was seen as longer than five metres. Dong e.a. indicated that Chungkingosaurus strongly resembled Tuojiangosaurus, found in the same formation, in many anatomical details. Chungkingosaurus was different in its smaller size, deeper snout and front lower jaws (resulting in a relatively high and narrow skull), and non-overlapping teeth with less pronounced denticles.
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The pectoral fins are narrow and sickle-shaped, and particularly long in adults. The anal fin originates slightly ahead of the second dorsal fin and has a deep notch in the posterior margin. The caudal fin is fairly high with a well- developed lower lobe. The skin is densely covered by minute, overlapping dermal denticles.
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The cycle repeats with a new bulge. These elements tend to grow evenly thus yielding a rectangular shape. In contrast, other species such as H.typicalis of H. latidentatus have a sloped lateral profile because the posterior section slopes downward. New denticles form near the posterobasal corner and grow gradually upward but also to the side.
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The dermal skeleton is organized in three layers: a superficial lamellar layer, a cancellous spongiosa, and a compact basal lamellar layer. Even in early ontogeny, these layers are apparent in specimen of Bothriolepis canadensis. The compact layers develop first. The superficial layer is speculated to have denticles that may have been made of cellular bone.
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Two Oceans: a guide to the marine life of southern Africa The labrum is broad and robust, with 15 to 19 pigmented denticles. The aperture is narrow and may be constricted towards the rear.Liltved, William Rune. Cowries and their relatives of southern Africa: A study of the southern African Cypraeacean and Velutinacean gastropod fauna, Gordon Verhoef, Seacomber Publications, 2000.
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The gonothecae are generally ovate in shape and slightly rugose in texture. A raised tubular structure with four vertically projecting denticles surrounds the aperture. Although the male and female gonothecae are similar in shape the male is considerably smaller and is white, whilst the female is yellow in colour. Colonies are typically 40–50 mm in height.
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Myrmecridium is a genus of fungi in the class Sordariomycetes. Circumscribed in 2007, it is distinguished from similar fungi by having entirely hyaline (translucent) vegetative hyphae, and widely scattered, pimple-shaped denticles (toothlike projections) on the long hyaline rachis. The generic name derives from a combination of the Ancient Greek wordmyrmekia, meaning "wart", and the suffix -ridium from Chloridium.
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The caudal peduncle is thin and bears slight lateral keels. Males have shorter abdomens and longer caudal peduncles than females. The caudal fin is broad and triangular, with nearly symmetrical upper and lower lobes and a prominent notch in the trailing margin of the upper lobe. The dermal denticles are flattened and not toothed or elevated on stalks.
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The anal fin is absent. There is a strong ridge running between the pectoral and pelvic fins on each side of the body. The dermal denticles are large and widely spaced, giving the skin a very rough texture. This species differs from the similar sailfin roughshark in the positioning of the dorsal fins and the shape of the spiracle.
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The facial suture (almost) coincides with the frontal glabellar furrow. Eye smaller, staying clear of the lateral and posterior border furrows. The hypostome is about as wide as long with three blunt denticles. Tips of the thorax segments point increasingly further backwards as these are situated nearer to the pygidium with the last one pointing parallel to the midline.
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It is brownish above and white below, and lacks dermal denticles. Benthic in nature, the sixgill stingray is usually found over upper continental slopes and seamounts at depths of . It has been recorded from scattered locations in the Indo-Pacific from South Africa to Hawaii. This species probably uses its snout to probe for food in the bottom sediment.
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The head was small. It had small leaf-shaped cheek teeth (triangular and with small ridges and denticles lining the front and back edges), and premaxillary teeth with less ornamentation. Like several other neornithischian dinosaurs, such as Hypsilophodon, Thescelosaurus, and Talenkauen, Nanosaurus had thin plates lying along the ribs. Called intercostal plates, these structures were cartilaginous in origin.
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The closest relative of Thaumatichthys is Lasiognathus, which also possesses enlarged, hinged premaxillaries, denticles on the esca, and a branched upper operculum. There are also significant differences between the two genera though, and Lasiognathus shares many more traits with the family Oneirodidae (in which it was formerly placed) than does Thaumatichthys.Pietsch, T.W. (2005). Thaumatichthyidae. Wolftrap Seadevils.
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The teeth of Patagosaurus are reminiscent of more derived sauropods. They are similar in morphology to Euhelopus, being concave on one side as well as having crowns with fairly great expansions. They are also similar to Camarasaurus, although the latter genus has less of a concavity and expansion. The teeth also possess marginal denticles on the crown.
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Adult males have stubby claspers. There is a single rounded dorsal fin positioned over the pelvic fins. The short and thick tail has a skin fold running along either side and terminates in a large triangular caudal fin with rounded corners, which is almost symmetrical above and below. The soft skin is completely devoid of dermal denticles.
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The rough longnose shark (Deania hystricosa) is a little-known deepwater dogfish. This species was described by Samuel Garman in 1906 and originally named Acanthidium hystricosa. The rough longnose dogfish has an extremely long snout, no anal fin, small grooved dorsal spines, and rough, pitchfork-shaped dermal denticles. The first dorsal fin is long and narrow.
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Sensory sulci (canals running along the surface of the skull) are present in many temnospondyls but are hardly visible on lydekkerinid skulls. The infraorbital sulcus, a canal that runs below the eyes and nostrils, has a distinctive bend along its length. Small bumps called denticles cover much of the palate. Lydekkerinids are usually classified as basal stereospondyls.
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The columella, concave in its upper part, is coated with an enamel whose edge rises in a blunt crest. Starting at this ridge, pointing inwards, are 8 folds regularly spaced along the length. The outer lip is convex, strongly thickened; Its sharp edge is not prominent. The folds in the interior protrude in the form of strong denticles.
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Incilius holdridgei tadpoles are small in size with ovoid-shaped bodies that are dark brown in color and feature a lighter venter surface. The tail and caudal fins are rounded. The mouth is directed ventrally and the oral disc has beaks and 2 to 3 rows of denticles which are bordered by a row of large papillae.
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The skin is completely devoid of dermal denticles even in adults. The disc is yellowish gray-brown above, with irregular darker blotches and yellow marks adjacent to the eyes and spiracles; the underside is white with irregular darker spots and a yellowish gray margin. The tail is dark brown with a yellow lateral stripe and black fin folds.
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Its pygidium is subcircular, with its apex turned under. The median lobe of its genitalia has a total length of 0.27 mm; its ventral valve is subtriangular and rather sclerotised, bearing sensilla and a row of 10-13 setae on each side. Its internal sac possesses 2 or 3 pointed denticles. The apex of its parameres contain abundant setae.
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The serrations are formed from individual denticles, each of which is further denticulated. On both the labial (outer) and lingual (inner) surfaces of the tooth, there is a deep central groove running longitudinally. The grooves form deep invaginations that constrict the inner pulp cavity of the tooth. The grooves do not reach the tip of the tooth.
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A study by Octávio Mateus e.a. in 2009 recovered Kentrosaurus in a basal position in the Stegosauridae as shown by this cladogram: Earlier analyses had shown Kentrosaurus closer in the tree to Stegosaurus. Basal traits include a prominent paraquadratic foramen at the quadrate in the skull; maxillary teeth with only seven denticles at the margin; and a shoulder spine.
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This stingray attains a maximum known length of and a disk width of . It has a rounded pectoral fin disk and a broadly angled snout with a small protuberance at the tip. The tail lacks fin folds but has a low ventral keel. The dorsal surface of the body and tail are covered with rough dermal denticles.
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The tail is stout, bearing a serrated stinging spine, and terminates in a rounded caudal fin. The pelvic fins have abruptly rounded tips. The teeth have narrowly oval bases and no elevated cusps. The dorsal surface is covered uniformly by dermal denticles on stellate bases, becoming larger towards the midline of the disc; the underside is smooth.
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The permanent dental formula for Zygorhiza is , the deciduous dental formula is . The cingula at the base of the tooth crowns on P2–4 are strongly developed but do not meet on the medial side. P2, the largest upper tooth, has four accessory denticles on the anterior and posterior cutting edges. P3–M2 form a closed series.
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The tail ends in a leaf-shaped caudal fin, whose dorsal origin lies behind the ventral origin. The skin is devoid of dermal denticles, though there are tiny white bumps on the upper central portion of the disc. This species is dark brown above, with many indistinct darker and lighter spots, and pale below. The sole specimen measures long.
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The tail measures less than an eighth as long as the disc and is moderately flattened at the base, tapering smoothly to a lance-shaped caudal fin. There are no dorsal fins or fin folds. A single, serrated stinging spine is placed atop the tail, well behind the base. The skin is devoid of dermal denticles.
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The 16 longitudinal ribs and the transverse lirae (5–6 in the penultuimate whorl, 18–20 in the body whorl) are produced into acute nodules at the points of intersection. The small aperture is narrow. The outer lip is slightly incrassate, distinctly sinuate and shows about six small denticles inside. The wide siphonal canal is very short.
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Griphognathus ("hook-jaw") is an extinct genus of lungfish from the late Devonian period of Europe and Australia. Griphognathus was a specialized lungfish, about long, with an elongated snout. The lower jaw and palate were lined with tooth-like denticles. Like all other lungfish, its skin was covered by overlapping scales, and it had an asymmetrical tail.
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Recent reports indicate the graytail skate grows to a length of approximately , with a maximum reported length of . The disc width is generally less than the total length, growing to a maximum width of approximately . An earlier study found mature individuals to be considerably smaller. The dorsal surface is black-brown and is covered by denticles but lacks spines.
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The undulate ray features a disc-shaped body, triangular in the front and near-circular in the rear, and dermal denticles developed as spines for protection. Median spines are scattered in adults, regular on young. The males have one lateral row each side, whereas the females have three. The eyes are medium-sized and followed by spiracles.
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Larger rays also gain a mid-dorsal band of heart-shaped, flattened denticles. The coloration is olive, brown, or gray above, sometimes with darker spots, and yellowish to white below; the keel and fin fold on the tail are black. This species reaches a maximum known disc width of , though is more typical. Females grow larger than males.
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A subtle dorsal keel and low ventral fin fold are present behind the spine. There is a row of 30 tubercles along the midline of the back, and another row of 16 tubercles in front of the spine. The tail behind the spine is covered by small denticles. The coloration is light brown above and white below.
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Heliobatis ranges from in length, with an average of between . As in modern stingrays the genders are dimorphic, with males possessing claspers. Heliobatis individuals have up to three modified dermal denticles, forming barbed stingers, on their tails, though individuals are often found with less than three. The genus is considered to have been demersal in nature.
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Like the rest of the skull, tooth preservation on the jaw is too poor to conclude much about its dentition. However, it is clear that the first of the coronoids (a series of bones adjacent and inwards of the main tooth row) was toothless, in contrast to Eobaphetes and Eogyrinus, which have denticles on the first coronoid.
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Their narrow skull along with their serrated teeth allow allosauroids to better slice flesh off of their prey. Allosauroid teeth are flat and have equally-sized denticles on both edges. The flat side of the tooth face the sides of the skull, while the edges align on the same plane as the skull.Infante, P., et al.
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The denticles here were compressed and directed towards the top of the crowns. Both the outer and inner side of the tooth crowns bore enamel, and both sides were divided vertically by a ridge. Each edge had about seven or eight denticles, with the front edge usually having the most. The skull of Stegoceras can be distinguished from those of other pachycephalosaurs by features such as its pronounced parietosquamosal shelf (though this became smaller with age), the "incipient" doming of its frontopariental (though the doming increased with age), its inflated nasal bones, its ornamentation of tubercles on the sides and back of the squamosal bones, rows of up to six tubercles on the upper side of each squamosal, and up to two nodes on the backwards projection of the parietal.
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Towards the front of the tooth, the ridged part is separated from the carina (cutting edge) by an area that is slightly concave front to back. The only similarities between MB R 1084 and the Middle Dinosaur Member teeth lie in their general shape and density of their serrations, as all teeth have 10 denticles per on the rear carina and 13 denticles per on the front carina. In a 2012 paper, Buffetaut used MB R 1084 as the holotype specimen for the new genus and species Ostafrikasaurus crassiserratus, describing it as an early spinosaurid theropod. Its generic name is derived from the German name of the colony in which the fossils were found, Deutsch-Ostafrika, meaning "German East Africa", combined with the Greek σαῦρος ('), meaning "lizard" or "reptile".
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These were designed by Matthew Poloso and Sherl Winter, respectively. These first four medallions bore no notation of their metallic content or country of origin. This was done to distinguish them from federal coinage. Beginning in 1982, this information and small, toothlike designs, known as "denticles", were added along the inner rim of the medallions, and reeding was added to the edge.
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Additionally, gastroliths may have had a variety of functions instead of being limited to just one. Stomach contents of Tatenectes include the hooklets of coleoid cephalopod and teeth and denticles from a small hybodont shark, indicating that Tatenectes fed on these animals. These prey items show that Tatenectes was not a bottom feeder, unlike some elasmosaurids as indicated by their stomach contents.
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The anal fin is absent. The tail is slender, leading to a long caudal fin with a small lower lobe and a low upper lobe with a prominent ventral notch near the tip. The dermal denticles are thin with hooked tips, arranged without a regular pattern well-separated from one another. The coloration is brown above, abruptly transitioning to black below.
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The first three teleoconch whorls contain spiral cords and axial folds, which fade out on the next two except for the subsutural spirals. The body whorl resumes a spiral sculpture of very even, flattened cords much that are broader than the interspaces. The aperture is lanceolate. The outer lip is slightly thickened externally and bears 5–6 strong rounded denticles inside.
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It has the typical shark coarse dermal denticles, but these are atypically large for the size of the shark. It contains small, circular spiracles at the dorsal base of its head. The supraorbital ridges are not expanded and do not form a knob in front of the spiracles. It has lanceolate upper teeth, containing 12 rows and lower bladelike teeth containing 12 rows.
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They are crossed regularly by numerous, fine spiral lirae, producing granular or transverse plicules. The aperture measures about a third of the total length. The weakly notched siphonal canal is narrow and shallow. The sharp outer lip is denticulate on the inside and usually shows a particularly strong tooth close to the well-cut anal sinus. The columella occasionally carries 1-2 denticles.
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The genus is characterized by elongate mandibles bearing a series of minute peg-like denticles that arise behind the masticatory margin, by frontal lobes that are poorly expanded laterally, by large and deep antennal fossae, and by pedunculate petiole, with a poorly defined node. Among Lenomyrmex species, the queen caste has been described only for L. mandibularis, L. wardi and L. inusitatus.
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The skin is delicate and entirely lacking dermal denticles. The disc is purplish to pinkish brown above, darkening slightly at the fin margins; the skin is easily abraded, leaving white patches. The underside of the disc is white with dark margins on the pectoral and pelvic fins. The snout is translucent, and the tail and caudal fin are almost black.
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The males are small and slender, with greatly enlarged olfactory organs, long hooked denticles at the tips of the jaws, and no esca. The skin is a uniform dark brown with small spines throughout. As the male matures, the body and head become less deep and the jaws become more prolongated. The largest known male specimen measured 45 mm long.
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Richardson's ray (Bathyraja richardsoni) is a skate of the family Arhynchobatidae, found in the Atlantic Ocean and around Cook Strait in New Zealand, at depths of from 1,300 to 2,500 m. Their length can reach 1.75 m. Dorsal and ventral surfaces of the disc are uniformly covered with dermal denticles, but lack thorns on the disc. The tail has 18 moderately sized thorns.
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Elevated paired nasal crests are shared with Allosaurus. Denticles continuing over the tooth apex are today known from other species. In 2015, it was reported that the front of the snout of Neovenator contains a complex system of neurovascular canals, functioning as sensory organs. This trait is also known from Spinosauridae and was there explained as an adaptation for searching prey in water.
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The dorsal surface and basal portions of pelvic fins have brown spots on a light brown background. Three brown streaks are noted on the posterior distal pectoral fins. Ventral surface is pale brown, with no variation noted. Dorsal areas are covered in dermal denticles except for two symmetric patches on the disc and along the posterior margin of the pectoral and pelvic fins.
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The dorsal margin of the maxilla is unusually concave unlike the convex condition in tyrannosaurids. The nares are large and elliptical, supporting its relation to proceratosauridae. The dentary gradually curves upwards as it approaches its front edge. Many teeth are preserved attached to the maxillae, with a roughly equal number of denticles on each side, similarly to those of tyrannosaurids.
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The inner lateral is slender, narrowed toward the cusp, like the centrals, and (sometimes at any rate) bearing a lamella behind the peduncle. The outer laterals are very broad, with one or several denticles on the cusp. The only character separating Cantharidus from Gibbula is the simple cusp of the central tooth, whilst in Gibbula it is denticulate at the sides.
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Henodus, however, differs from other placodonts in having developed unique baleen-like denticles, which alongside features of the hyoid and jaw musculature suggest that it was a filter feeder.Rieppel, O. (2002). Feeding mechanisms in Triassic stem-group sauropterygians: the anatomy of a successful invasion of Mesozoic seas Zoological Journal of the Linnean Society, 135, 33-63Naish, D. 2004. Fossils explained 48. Placodonts.
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In Ancient Roman society, garum, a type of fish sauce condiment, was popular. Sharkskin and rayskin which are covered with, in effect, tiny teeth (dermal denticles) were formerly used in the same manner as sandpaper is in the modern era. These skins are also used to make leather. Rayskin leather (same'gawa) is used in the manufacture of hilts of traditional Japanese swords.
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The skin entirely lacks dermal denticles. This species is yellowish brown above, becoming slightly lighter at the lateral margins of the side, and white below; some individuals have irregular blotches and/or a dark stripe along the dorsal midline of the tail. The caudal fin becomes dark towards the tip. Males and females can grow up to and across respectively.
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There is no anal fin. The caudal fin is broad, with a well-developed lower lobe and a deep ventral notch near the tip of the upper lobe. The small dermal denticles have sharp wedge-shaped crowns bearing median ridges, and are placed on stalks (pedicels). This species is dark brown, with prominent blackish, then light bands at the fin margins.
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The short and thick tail bears skin folds along either side and two dorsal fins on top. The first dorsal fin is slightly larger than the second. The well-developed caudal fin is triangular with blunt corners, and is approximately as long as the space between it and first dorsal fin. The skin is smooth and soft, entirely lacking dermal denticles.
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Traditional shark fin soup or stew is made with fins obtained from a variety of shark species. Raw fins are processed by first removing the skin and denticles before trimming them into shapes and bleaching to a more desirable coloration. Sharks' fins are sold dried, cooked, wet, and frozen. Ready-to-eat shark fin soup is also readily available in Asian markets.
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The shells of Pupilla loessica are about 3 mm high, thin, cylindrical-ovate and have a rounded conical apex. The approximately 5 strongly curved whorls gradually increase in height and are finely and irregularly ribbed. The short elliptical aperture has no denticles, no palatal callus and is only slightly broadened. The crest is at most indicated by a weak band.
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The upper caudal fin lobe is longer than the lower lobe, and bears a notch in the trailing margin near the tip. The skin is covered by overlapping dermal denticles, each with three horizontal ridges leading to marginal teeth. This species is brownish gray to gray above and off-white below, and lacks fin markings. It grows up to long.
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Even as B. elegans growth progresses, it does not emit any noticeable odors. Normally, the species does not usually produce budding cells, however they can form on scattered giant cells. Hyphae are translucent, about 2-3 μm wide, grow outwards unevenly and septate every 20-40 μm. As cylindrical denticles continue to develop, conidia will form at their apical ends.
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The southern part of the temple is marked by double three-quarter columns, placed on pedestals and carrying an entablement. The protrusions of the liberated parts are full three-tiered, in the span are devoid of a tier of architrave. Under the frieze a row of curly denticles was launched. The wall of the wall is cut by windows in two axes.
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The shinbone has a vertical ridge on the upper outer side, the crista cnemialis, touching a lower vertical ridge, the crista fibularis. Photo and CT scan of skull PMOL-AD00102 There is a number of other notable traits. The upper branch of the praemaxilla excludes the maxilla from the nostril. The premaxillary teeth lack denticles; those on the maxillary teeth are small.
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Its maxillae have seven pairs of free denticles. It counts with two peristomial segments without setae. It counts with a cirriform acicular lobe, its supraacicular chaetae being simple, while the subacicular chaetae are compound, and exhibit serrated blades. Its pygidium has a terminal anus, with two pygidial cirri that measure as long as its antennae and shows a short appendage ventrally.
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The natural history of the leopard whipray is poorly understood, partly due to confusion with other species. It presumably preys on crustaceans and small fishes. Like other stingrays, it is aplacental viviparous, with the developing embryos sustained by histotroph ("uterine milk") produced by the mother. The newborns measure roughly across and long, smaller than in H. uarnak and H. undulata, and have few or no denticles.
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Chimaera monstrosa are fish that have distinct sex from birth. They reproduce by internal fertilization of male and female. For reproduction, C. monstrosa displays a small club like structure with a bulbous tip armed with numerous sharp denticles located on the top of the head. This structure is suggested to be used by male fish to grasp the pectoral fin of the female during copulation.
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Two much shorter rows of smaller tubercles, slightly converging backward, are found alongside the central row behind the shoulders. Numerous small dermal denticles are also found between the eyes and on the tail behind the spine. The dorsal coloration varies from plain reddish-brown to dark gray, and the underside is light. The extent of denticle coverage and number of oral papillae can vary among individuals.
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Its dermal denticles are also unusual, resembling the scales of a bony fish. This species typically reaches in length; sharks in the Mediterranean Sea are much smaller and have distinct depth and food preferences. Relatively common, the Portuguese dogfish is an active hunter capable of tackling fast, large prey. It feeds mainly on cephalopods and fishes, though it also consumes invertebrates and cetacean carrion.
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At birth, they are less than and they mature at about . Most records are of individuals less than , but they can reach about . Their litter size is seven or eight pups off Angola to 23 in the Mediterranean. They have ridges over their eyes that expand into large, rounded knobs, which are covered with enlarged denticles – these are absent in other species of rough sharks.
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The ligament is internal and no teeth occur on the hinge joint. The right valve has some small denticles on its margin which fit into grooves in the left valve margin. A single large adductor muscle holds the valves together, which leaves a large, kidney-shaped scar on the inside of each valve. The colour is purplish-brown on the outside of the valves.
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The caudal fin has a strong lower lobe and a long upper lobe with a prominent notch near the tip. The body is covered by small, non- overlapping dermal denticles; each denticle has radial ridges converging to a round central pit. The body is dark brown above and black below, with light margins on the fins. Small, light-emitting photophores are scattered over the body.
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A moderately rough covering of dermal denticles is present over the upper surface and both dorsal fins; the underside is mostly smooth, except along the pectoral and pelvic fin margins. This species is greenish brown above with many round, pale-edged brown spots, black saddles below the dorsal fin bases, and white pelvic fin edges. It is plain white below. The sole specimen measures long.
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Behind the premaxilla is the maxilla, which contains a small depression that forms part of the antorbital fossa. This depression distinguishes Yonghesuchus from related archosauriforms such as Turfanosuchus. As in other archosauriforms such as Turfanosuchus and Euparkeria, the palate is covered in very small teeth called denticles. Behind the palate, the basisphenoid bone (which forms the floor of the braincase) is long and narrows toward the front.
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Bythaelurus stewarti, the Error Seamount catshark, is a catshark of the family Scyliorhinidae in the order Carchariniformes. It is endemic to Error Seamount, a guyot located in the Arabian Sea in the western Indian Ocean. Its closest relative is the bristly catshark (B. hispidus), which it differs from in its larger size, darker and more mottled coloration, and especially its smaller and less densely concentrated denticles.
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Ventral areas smooth except for a few patches of denticles of varying density. The dorsal surface has a row of 31 thorns along the midline, and a parallel row of three on either side of the midline approximately mid-disc. It has additional thorns around the eyes and snout. The tail has an additional 29 thorns on the midline, and other thorns in regular and irregular rows.
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The first pair of appendages were small, lacking denticles, and the subsequent four pairs of appendages were likewise also small, but with fixed spines and serrated distal podomere margins. The sixth and last pair of appendages were short but were powerfully serrated on the anterior margins of the podomeres. The type A genital appendage was long and undivided, the type B appendage was more oval in shape.
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Unlike the better-known embolomeres, the baphetid cheek and skull roof are sutured together. There is a strongly embayed spiracular ("otic") notch, but the stapes is distally broad, which seems to rule out a sensitive hearing apparatus. The palate is closed—a primitive character, but very different from the temnospondyls. The coronoids bear no teeth or denticles, while the dentary has a double tooth row.
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The dermal denticles are small, narrow, and pointed, and cover the entire upper and most of the lower body surface. There are patches of small spines on the snout and over the eyes. Small individuals have a row of thorns down the middle of the back. The coloration is gray to reddish or greenish brown above, with many small black and white spots, and white below.
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The pectoral fins are moderately large. The short and broad caudal fin has a ventral notch on the upper lobe and an indistinct lower lobe. The skin is thick, bearing well-calcified leaf-shaped dermal denticles. The back is brown, with a distinctive pattern of H-shaped, dark brown saddles with well-defined margins, along with numerous small white dots and darker mottling between the saddles.
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There is a prominent fold of skin running along either side of the tail, and a serrated stinging spine placed on the upper surface about halfway along its length. There is no dorsal fin. The skin is completely devoid of dermal denticles. This species is uniformly light gray above with a darker V-shaped marking between the eyes, and white below with slightly darker lateral disc margins.
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The skin is devoid of dermal denticles. Rays found in the Coral Sea are generally light gray or brown above with tiny dark dots, while those off Queensland tend to be darker brown above and unpatterned. The dorsal and caudal fins are brown with blackish margins. Juveniles are usually more densely spotted than adults, and have a dark stripe along the dorsal midline of the tail.
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The short, very flattened tail measures 67-79% as long as the disc and terminates in a short, deep, leaf- shaped caudal fin. A lateral skin fold runs along the each side of the tail, which is most obvious in juveniles. The upper surface of the tail bears a rather large dorsal fin followed by a serrated stinging spine. The skin entirely lacks dermal denticles.
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There is a tentacle-like structure on the inner posterior margin of each spiracle. The tail is short and slender, measuring a quarter the disk width, with upper and lower fin folds. There are one or more serrated spines at the base of the tail. The skin is naked in juveniles and subadults, while adults develop a patch of denticles on the center of the disk.
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The main differences regarding geographic variation involve slightly distinct propodeal shapes, such as a shorter dorsal face in the Ecuadorian specimens. Specimens from Rondônia, Brazil, differ from other conspecific workers by their darker color (almost black) and more prominent propodeal crests that form small denticles. Given the similarity among the samples examined, Fernández, Feitosa & Lattke (2014) decided to consider these morphological differences as intraspecific variation.
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The elongated pectoral fins had denticles along the leading edge which may have had a role in mating. They are thought to have been able to move their pectorals in a vertical plane,”flying” through the water much like modern-day flying fish. The majority of iniopterygians are placed within the family Sibyrhinchidae. Members of this family include Sibyrhinchus denisoni, Inioptera richardsoni, and Inioxyele.
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The columella is cylindrical, with a groove round its upper part, running at its left side towards a square notch, formed by a square, toothlike fold at the basal part and the most proximal of the internal lirae of the base. Below the notch there are one large and two small denticles. The parietal wall is callous.Schepman 1908-1913, The Prosobranchia of the Siboga Expedition; Leyden,E.
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Diet is largely deduced by the tooth morphology, tooth marks on bones of the prey, and gut contents. Some theropods, such as Baryonyx, Lourinhanosaurus, ornithomimosaurs, and birds, are known to use gastroliths, or gizzard-stones. The majority of theropod teeth are blade-like, with serration on the edges, called ziphodont. Others are pachydont or phyllodont depending on the shape of the tooth or denticles.
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The evolutionary origin of the vertebrate dentition remains contentious. Current theories suggest either an "outside-in" or "inside-out" evolutionary origin to teeth, with the dentition arising from odontodes on the skin surface moving into the mouth, or vice versa. Despite this debate, it is accepted that vertebrate teeth are homologous to the dermal denticles found on the skin of basal Gnathostomes (i.e. Chondrichtyans).Martin et al.
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The first to eight denticles of originally twelve or thirteen are also preserved. The enlarged anterior denticle and the curvature present in the anterior margin of the coxal neck suggest an assignment to Acutiramus rather than other genera in Pterygotidae. However, B. horrida has not been formally synonymized with Acutiramus due to the lack of more diagnostic material, and therefore remains as a dubious name.
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Distinguishing characters of Supayacetus include: a T-shaped manubrium with a rod-shaped process; cheek teeth with accessory denticles; a broad scapula with a large infraspinous fossa; humerus with large and hemispherical head, well-defined proximal tuberosities, a long deltopectoral crest, and a broad shaft. Compared to other basilosaurids, Supayacetus is larger than Protocetus but its skull and vertebrae are smaller than in other basilosaurids.
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The pelvic fins are small, with elongate, relatively short claspers in males. The anal fin is substantially larger and deeper than the second dorsal fin. The caudal fin is deep, with a distinct lower lobe and a strong ventral notch near the tip of the upper lobe. The body is densely covered by minute dermal denticles, each shaped like an arrowhead and bearing a median ridge.
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The radula has seven denticles (or small teeth), which are sometimes reduced. The Mesogastropoda are, in many ways, more developed than the Archaeogastropoda. Through torsion of the intestinal mass and a spiral movement of the body, the gill, the kidney and the osphradium (which means sensory receptor, or olfactory organ) have disappeared on the right side. These organs exist only on the left side of the animal.
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One of its two dorsal fins is short in length but tall, while the other is lower and longer. Its caudal fin is long, and contains denticles on its upper lobe. It has a brown upperside and a more greyish-brown underside, with a white snout. The edges of the fins tend to be darker in color, ranging from a dark brown to purple color.
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The anal fin is smaller than the second dorsal fin. The dorsal surface of the caudal peduncle bears a crescent-shaped notch at the caudal fin origin. The asymmetrical caudal fin has a well-developed lower lobe and a long upper lobe with a ventral notch near the tip. The dermal denticles are small and overlapping; each has five horizontal ridges leading to marginal teeth.
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Aetiocetus is a small, toothed whale with no more than three small denticles on the anterior and posterior margins of the posterior upper teeth. Their postcanine teeth are somewhat heterodont. The base of the rostrum, or snout, of the whale, is greater than 170% of the width of the occipital condyles where the skull meets the neck. These features are synapomorphies, or shared derived traits, of Aetiocetus.
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The capsule surface is smooth with lengthwise striations, and opaque cream in color with yellow margins. Long, coiled tendrils extend from the four corners of the capsule. When the embryo is long, the external gills have been lost, the dermal denticles have begun to develop, and light brown saddles are present. The eggs take roughly one year to hatch; newly emerged sharks measure long.
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Their rims are stiffened with chitin and may contain minute toothlike denticles. These features, as well as strong musculature, and a small ganglion beneath each sucker to allow individual control, provide a very powerful adhesion to grip prey. Hooks are present on the arms and tentacles in some species, but their function is unclear. The two tentacles are much longer than the arms and are retractile.
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The skin is thick and roughened by well- calcified dermal denticles; each denticle is triangular and pointed. This species is light grayish brown to purplish above, including the upper surface of the pectoral fins, and paler below. A series of 6-7 faint darker saddles are present along the back and tail, which are more obvious in younger sharks. The fins lack obvious lighter margins.
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The shape of the alveolus situated on the anterior portion of the fragment suggests that it housed a tooth that was smaller and more circular than the others; an incisiform tooth which is common in tyrannosauroids. The disarticulated teeth recovered are transversely narrow, serrated (17–18 denticles/cm) and recurved. The femur is only 3% longer than the tibia. The longest manual ungual phalanx recovered measured in length.
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With no bioluminescent lure and an unusual tooth arrangement, it is unclear what the toothed seadevil feeds upon and how. It has been suggested that their external jaw teeth serve to entangle soft-bodied invertebrates. The males are fully parasitic, using tooth-bearing denticles at the tips of their jaws to attach to the female and their tissues and blood vessels becoming fused with that of the female.
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The aperture is bordered externally with a strong varix forming a rim, normally unique - not repeated at the earlier growth stages on the spire. The inner side of the outer lip bears ca. 10 denticles, elongated in the spiral direction. The parietal edge of the aperture forms a very thin, appressed callus, with a distinct adapical denticle, continued into a thicker columellar callus with a slightly raised edge.
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The height of the shell attains 10 mm. The rather thin, imperforated shell has a conical spire and rounded, inflated body whorl. The sculpture shows elevated spiral cords, slightly unequal in size and narrower than interspaces, crossed by minute and numerous prosocline lamellae which override the cords. The peristome is flaring in adult shells, with a distinct outer varix and with internal denticles elongated in the spiral direction.
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Adult sleeper rays range in size from 8 to 46 cm in length and have flattened oval, circular, or pear-shaped pectoral fin discs. They have naked skin, without dermal denticles or thorns. The snout is moderately elongate and broadly rounded, with the rostal cartilage reduced to a slender medial rod. This distinguishes the narkids from the family Narcinidae, which have somewhat longer snouts supported by broad rostral cartilages.
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The tail terminates in a fairly large, triangular caudal fin about as long as wide, with rounded corners. The skin entirely lacks dermal denticles. This species is plain light brown dorsally, sometimes with darker markings and whitish spots, and pale ventrally, with broad darker margins on the pectoral and pelvic fins. Possibly the smallest cartilaginous fish, the smallest known adult finless sleeper ray measured only long and weighed .
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The first coins that featured the image of the RCMP were the twenty-five cent and one dollar coins of 1973. Police Constable Paul Cedarberg designed both coins. The twenty-five cent coin is unique in that there are two varieties of the coin. A new obverse with a smaller, more detailed portrait and fewer rim denticles placed farther from the rim was planned for use with the RCMP commemorative reverse.
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The arachnoid appearance is common on the leaves and stems of various sclerophyllous members of the Asteraceae, such as some thistles. Nonetheless, "cobwebbiness" is a subjective impression, and in the likes of Hayworthia arachnoidea the arachnoid impression arises from the thicket of spinescent leaf denticles that are not at all fine, tangled, or fragile. In the cactus Cephalocereus senilis, the arachnoid effect arises from long-lasting hairy spines.
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The dermal denticles are flat and blocky, not elevated on stalks or bearing marginal teeth. The coloration is dark brown to black, with light fin margins. The underside is densely carpeted by light-emitting photophores, which extend to the tip of the snout and around the eyes and nostrils, and thin to almost non-existent on the back. This species has on average only 60 vertebrae, the fewest of any shark.
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Those in the mandible (lower jaw) have a thin, serrated tip and are relatively small and triangular (somewhat fang-like). Between 13 and 15 teeth are on either side of the symphysis. The teeth in the upper jaw are triangular, but much larger and broader with entirely serrated edges—14 or 15 occur along each side of the symphysis. The denticles lie flat and typically have between five and seven ridges.
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Columella multiplicate, with combined total 2 to 8 plications plus parietal lirae, rarely to 17 in which the posteriormost are denticles; one species with only 1 plication. Plications usually occupying less than half the length of the aperture, but most of the aperture in some. Plications excavated just inside aperture in a few species, usually evenly rounded, first plication usually raised and very strong. Shell with cystiscid internal whorls.
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The anal fin is much smaller than the dorsal fins. The caudal fin is relatively short and broad, with an indistinct lower lobe and a ventral notch near the tip of the upper lobe. The skin is thick and covered by well-calcified dermal denticles. Extremely variable in coloration, the coral catshark lacks prominent saddle markings but rather has many black and white spots on a grayish background.
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Figaro is a genus of catshark, and part of the family Scyliorhinidae. Until 2008, Figaro was generally considered to be a subgenus of Galeus (sawtail catsharks). The two known species are found off Australia, inhabiting deep, offshore waters on or near the bottom. Figaro contains small, slender, firm- bodied sharks that bear distinctive crests of enlarged, spiny dermal denticles along the dorsal and ventral edges of their short caudal fins.
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The formula of the radula is like this: 2 7 7 \+ + + + 2 7 7 Teeth are as in the other members of the genus. There are four perfect lateral teeth and the first marginal tooth is similar but with a second outer cusp. From this point the marginals become wider, the inner cusp remains always the larger, and the outer cusp develops from five to seven small cusps or denticles.
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The tail is flattened at the base and tapers rapidly, measuring 63-70% as long as the disc. There is a serrated stinging spine placed atop the tail about midway along its length, which is preceded by a low dorsal fin. The tail may also have slight ridge of skin running along each side, and terminates in a very short, deep, leaf-shaped caudal fin. The skin entirely lacks dermal denticles.
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The broad, triangular pectoral fins originate at or slightly before the level of the fifth gill slit. There is no ridge between the first and second dorsal fins. The lower lobe of the caudal fin is half the length of the upper, which has a strong notch near the tip. The dermal denticles are small and overlapping, usually with 7 horizontal ridges, giving the skin a smooth feel.
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A 2013 study argued that Gerrothorax consumed prey using suction feeding. Gerrothorax had strong muscles capable of both raising the cranium and lowering the jaw rapidly. The robust internal gill apparatus would have expelled water through the gills during this motion, creating intense pressure in the throat that would suck in small prey items. The gill arches were also covered in small denticles, prohibiting any prey from escaping once devoured.
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This is similar to the size ridges seen on Kentrosaurus. Like all stegosaurians, the denticles on the teeth are rounded at the tips, in contrast to ankylosaurians. Also, like Huayangosaurus, but unlike Kentrosaurus and Stegosaurus, Paranthodon possesses a prominent buccal margination (a ridge beside the tooth row). Paranthodon teeth preserve wear, but wear is absent on most teeth, similar to Huayangosaurus, meaning it is likely that Paranthodon lacked occlusion between teeth.
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The only described material of A. laaroussii are dentaries, maxillae, a premaxilla and several teeth. They broadly resemble A. madagaskarensis in general form but with a few distinguishing differences. The tooth count of A. laaroussii is higher, with 15–16 teeth in the maxilla compared to the 11–13 of A. madagaskarensis. The teeth of A. laaroussii are also taller than those of A. madagaskarensis and have more closely packed denticles.
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This opacity being caused by a dead-white transverse band crossing the few, coarse, prominent ribs and becoming broader in the body whorl. The aperture is narrow. The outer lip, under a lens, is very beautiful, being minutely warted, and with four denticles, the columellar margin with four plaits.Melvill J.C. & Standen R. (1895) Notes on a collection of shells from Lifu and Uvea, Loyalty Islands, formed by the Rev.
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The overall morphology of the conidia of C.arxii are very similar to Cladophialophora devriesii the conidial chains of C.arxii are longer. Additionally, the conidial chains are fragile and borne on denticles. The conidia of C.arxii are pale brown, smooth, thick walled with a lemon-spindle shaped morphology. Initially the fungus contained muriform cells from tissue samples but following corticosteroid therapy the cells changed their shape and become irregularly shaped hyphae.
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The tail behind the spine is covered by small thorns. The dorsal band of denticles is largely developed by the time the juveniles are across. The coloration of the reticulate whipray varies substantially with age and locality. Adults generally have a dorsal pattern of numerous closely spaced dark brown spots or reticulations on a beige to yellow-brown background, which becomes blackish past the spine with lighter bands on the sides.
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The "palate" (or hypostome), also only visible from the ventral side, is subtriangular (about as long as wide) and adorned with three weak denticles at its back rim. To the front the hypostome has weak wings extending sideways. The thorax consists of 11 segments. The tips of the segments are pointed and angle back increasingly from about 30° for the anterior segment to slightly pointing inwards for the posterior segment.
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Filter feeding habits are conspicuously rare among Mesozoic marine reptiles, the main filter feeding niche being seemingly instead occupied by pachycormid fish. However, some sauropsids have been suggested to have engaged in filter feeding. Henodus was a placodont with unique baleen-like denticles and features of the hyoid and jaw musculature comparable to those of flamingos. Combined with its lacustrine environment, it might have occupied a similar ecological niche.
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The dorsal surface is covered by small, roughly conical dermal denticles. This species is grayish brown above, darkening around the eyes and on the snout and becoming translucent at the trailing fin margins. There are blackish saddle markings below the dorsal fin bases, and sometimes also large, dark blotches and "eyespots" scattered over the dorsal surface. The underside is almost completely white, with a black leading margin on the pectoral fins.
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The first dorsal fin originates over the pelvic fins, while the second dorsal fin originates over the anal fin. The caudal fin is nearly horizontal, with an indistinct lower lobe and a prominent notch near the tip of the upper lobe. The skin is relatively smooth, as the dermal denticles are small and flattened. The coloration consists of a plain dark background with 7-8 darker, more or less prominent saddles.
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Denticles varied in length along the ridge and formed a kind of undulation in the edge of the tooth. The first tooth protruded from the premaxilla, while the mandibular symphysis (the part of the jaw in which both rami meet) was very long and had more than ten tooth sockets on each side. The face was long and straight, devoid of any lateral expansion. Teeth and mandible of Makhaira rossica.
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It can be readily identified by the large, thorn-like dermal denticles scattered over its body, some of which may be fused together. It is purplish brown or black in color and grows up to long. The diet of the bramble shark includes smaller sharks, bony fishes, and crabs, which this slow-moving species may capture via suction. It is aplacental viviparous, with females producing litters of 15–52 pups.
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This species is aplacental viviparous; females have two functional ovaries and two uteruses. Recorded litter sizes have ranged from 15 to 52, and newly born pups have been estimated to measure long. The dermal denticles in near-term embryos are underdeveloped, appearing as minute spines located within open pits in the skin. The size at sexual maturity is uncertain; the smallest known mature males and females are and long respectively.
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However, H.parvus is differentiated by the presence of cusps that are two times longer than the surrounding denticles. There are also transition forms that have apparatus features of both H.parvus and H.latidentatus which provide evidence of H.parvus being derived from H.latidentatus. There is also evidence to suggest that most species of Hindeodus likely evolved from H.typicalis and an unnamed species H.n.sp.B that were alive in the early Changsingian.
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The upper edge has a wide notch while the lower edge has a convex rounded outline. The lower margin hosts about thirty denticles, mostly in a single rough, though in some sections two rows are present. On the pronotum the spiracle opening is located at the top of a small projection. The petiole has a node shaped outline, with a rounded upper outline and a front facing projection on the underside.
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Dorsal and ventral view Almost circular in shape, it grows up to in disc width and in weight. The upper surface is covered with denticles (sharp tooth-like scales). The coloration is light brownish with mottled patterns on the dorso, and pink on the ventral side. As with all stingrays, the mouth and gill openings are on the underside, and the eyes and gills exits are on the dorsal side.
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The formula of the radula is 2·1·1·1·2. The central tooth is subquadrangular, multicuspid; the central cusps are very long and sharp; lateral teeth are multicuspid, marginals are narrow, with a few obsolete denticles on the margin. Species in the genus Velutina resemble the pulmonate genus Otina, but Velutina are strictly marine. Sometimes they are found out at sea, but usually live among stones near low tide.
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The caudal peduncle bears a crescent- shaped notch at the upper origin of the caudal fin. The asymmetrical caudal fin has a well-developed lower lobe and a long, narrow upper lobe with a ventral notch near the tip. The prominent lateral line curves downward below the second dorsal fin. The skin is densely covered by small, overlapping dermal denticles; each bears five horizontal ridges leading to marginal teeth.
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The smaller denticles taper to a point. Up to half the body length is taken up by the long upper lobe of the caudal fin, which is broader than in other threshers. The large pectoral fins have a curved anterior margin and broad tips. The first dorsal fin is placed further back than in the other thresher sharks, with the free rear tip located above or just before the pelvic fins.
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Schoch & Milner (2014) listed seven features in the diagnosis of Ecolsonia: (1) tabular and squamosal frame otic fenestra; (2) prefrontal and postfrontal separated (shared with most other trematopids); (3) preorbital region of equal length to posterior skull table; (4) vomer with a posteromedial process meeting the pterygoid (shared with other trematopids); (5) a supratemporal that is twice as long as it is wide; (6) triangular patch of denticles on the parasphenoid (shared with other trematopids); and (7) basipterygoid region unsutured (shared with some other trematopids). Trematopid synapomorphies include the posterior process of the vomer, the denticles on the parasphenoid, and the supinator process of the humerus. A large number of small scales were also found with some specimens of Ecolsonia that probably covered the entire body, a feature similar to that seen in the trematopid Anconastes; these are distinct from the osteoderms of dissorophids that are only associated with the vertebral column.
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Life reconstruction of Langstonia Due to the fragmentary remains generally known for this family, its possible only describe some general aspects of the appearance and biology of Langstonia. As mentioned above, the fossil type of the species is larger than Sebecus icaeorhinus with jaws and teeth even more flattened, although its general proportions are reminiscent of this species, which suggests that their skull would be higher and laterally flattened, in contrast to modern crocodilians, which generally have a horizontally flattened skull with conical teeth. Teeth are of the zyphodont kind, with very flattened sides, slightly curved back and with serrated edges with small denticles (between 5-6 denticles per millimeter in the teeth of this genus) and also without any grooves on its surface. This type of teeth appears in the close relatives of sebecids, the peirosaurids and baurusuchids of the Cretaceous and some crocodilians of the Cenozoic as the pristichampsids and some mekosuchines.
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The species within Atherion are characterised by having rough, sharkskin-like denticles around the mouth and in other places on the head. The origin of the first dorsal fin is to the rear of the pelvic fin tip. The first dorsal fin has 3–6 spines while the second dorsal fin has a single spine and 8–13 soft rays. The anal fin also has a single spine and has 13–17 soft rays.
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The hairs on the head have short denticles, and the antennae have three apical sensilla, each containing a somewhat bulky spinule. Young larvae are much smaller than sub-mature larvae at long. They appear similar to sub-mature larvae, but the diameter differs, gradually decreasing from the fifth somite to the anterior end. The hairs measure , with the longest found on the flagelliform and on all somites; the hairs on the somites, however, become sparse.
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The anal fin is larger than the second dorsal fin. There is a crescent-shaped notch on the caudal peduncle just before the origin of the upper caudal fin lobe. The asymmetrical caudal fin has a well-developed lower lobe and a longer upper lobe with a ventral notch near the tip. The skin is densely covered by overlapping dermal denticles, each bearing three to five horizontal ridges leading to marginal teeth.
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The placoid scales of cartilaginous fishes are also called dermal denticles and are structurally homologous with vertebrate teeth. It has been suggested that the scales of bony fishes are similar in structure to teeth, but they probably originate from different tissue. Most fish are also covered in a layer of mucus or slime which can protect against pathogens such as bacteria, fungi, and viruses, and reduce surface resistance when the fish swims.
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The tail is not quite as long as the disc, and is broad and flattened from its base to the stinging spine. The tail spine of one specimen examined measured long and bore 75 serrations. After the spine, the tail abruptly becomes thin and cylindrical, with a low, thick fin fold running underneath. The upper surface of the disc is covered by many large dermal denticles with star-shaped bases, concentrated on the snout.
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The so-called "brush" is not fibrous as was originally believed, but consists of a number of parallel, membranous tubules made of globular calcified cartilage. The brush base and basal plate are covered in a thin, acellular bone layer. Zangerl asserts that these tubules are similar to erectile tissues in humans, and thus the complex may have been inflatable. The complex itself is covered in up to nine rows of large denticles pointing anteriorly.
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The skin, excluding on the fins, is densely covered with irregularly arranged, nonoverlapping dermal denticles. Each denticle has a swollen rhombic shape with 10–40 facets on the crown. The viper dogfish is black with distinct darker markings on the underside. These markings contain large numbers of tiny light-producing photophores; more photophores are found sparsely scattered over the rest of the body, as well as in a translucent patch on the upper eyelid.
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It is in the genus Selaginella and this creeper is characterized by having flattened stems, bearing four rows of ovate leaves which vary in size according to their position. Its specific epithet, "denticulata" comes from the Latin "dens" which means tooth, and alludes to the denticles that appear on the leaves. It was identified by the nineteenth century botanist Antoine Frédéric Spring. It is distributed throughout the Mediterranean region except for the Cape Verde islands.
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121 Sinocalliopteryx is distinguished from Huaxiagnathus, as well as other compsognathids, by its relatively long hands in relation to its arms. The arms and hindlimbs were also longer overall than in other compsognathids, a feature possibly related to its size. Restoration Sinocalliopteryx had an elongated head with a pointed snout, showing a convex upper profile. There were four teeth in the premaxilla which were small but exceptionally had denticles on their front edges.
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This species was described by David Starr Jordan and Edwin Chapin Starks in 1901 from a type locality of Misaki in the Kanagawa Prefecture in the coast of the Sagami Sea in Japan. Jordan and Starks gave it the specific name elymus as the rough denticles around its mouth bear a resemblance to the seed heads of the rye grasses of the genus Elymus. It is the type species of the genus Atherion.
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Denticles are also present on the back and sides of the tail, at the base and behind the sting. In life, the back is covered by a thick layer of mucus. The dorsal coloration is plain olive to brown, becoming pinkish towards the disc margins and on the pelvic fins, and darkening to almost black towards the tip of the tail. The underside is nearly white, becoming pinkish towards the fin margins.
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The external surface form an intritacalx (= the chalky outer layer) which gives it a chalky appearance, even on fresh specimens, as is characteristic of the genus. The body whorl has maximum convexity just below the deep suture. Then it is rather parallel sided at the periphery and markedly constricted around the siphonal canal. The aperture is strongly thickened externally by the last varix, with an indistinct inner rim, bearing 5 faint denticles on aged specimens.
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The pelvic fins are small and angular; males have very long claspers. The caudal fin is low, with a distinct lower lobe and a strong ventral notch near the tip of the upper lobe. The dermal denticles are widely spaced, with three points and a median ridge. The dorsal coloration is distinctive, consisting of a grayish brown background with six pale-edged dark saddles along the body and two on the tail.
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There is a stinging spine on the upper surface of the tail, and a fin fold underneath measuring 60-67% the disc width. Young individuals have small dermal denticles in the middle of the back, whereas adults have a row of tubercles along the midline of the back and tiny thorns covering the tail. The coloration is yellowish brown above, becoming darker on the tail fold, and light below.Nishida, K. and K. Nakaya (1990).
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The description of Antarctilamna prisca includes material derived from both Antarctic and New South Wales localities, the prior comprising the holotype, a partial decayed carcass with dermal denticles, a fin spine and teeth preserved. Material from New South Whales comprises isolated spines. On this basis the authors proposed a tentative correlation between the lower part of the Aztec Siltstone of South Victoria and the Bunga beds of the New South Wales south coast.Young,G.C., 1982.
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The tail also has no venomous stinging spine, unlike other members of the family. A dense patch of flattened, heart-shaped dermal denticles covers the center of the disc and extends onto the tail. Larger individuals additionally have numerous tall, sharp thorns over the entire upper surface of the disc. The porcupine ray is plain light to dark gray or brown above, darkening to blackish towards the tail tip, and white below.
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The caudal fin is broad and triangular, with fairly angular corners and a nearly straight trailing margin. The skin completely lacks dermal denticles. This species is a plain reddish to orange brown above, with a very thin pale posterior margin on the dorsal and caudal fins. The underside is light cream, with darker reddish coloring along the pectoral and pelvic fin margins, outlining the ampullae of Lorenzini, and as blotches under the tail.
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The tail past the sting is uniformly covered by denticles. The lateral line network is well-developed both over and beneath the disc. Smaller rays are plain greenish gray above, while larger rays are yellowish brown; the tail is uniformly brown and lighter in front of the sting. The underside is distinctively bright yellow, with a thin dark border around the disc margin and sometimes darker blotches around the nostrils, mouth, and gill slits.
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The mandible of Limnoscelis was well-built, with large processes for jaw muscle attachment, indicating that it had a powerful bite. In addition to its premaxillary, maxillary, and dentary teeth, Limnoscelis had additional palatal teeth on transverse flanges of its pterygoid. These flanges consisted of an anterior row of smaller blunt denticles, and a posterior row of larger teeth, with neither having labyrinthodont infolding. The pterygoid of Limnoscelis articulated with the basisphenoid.
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The postorbital bone is rounded and smoothly crescent-shaped, in contrast to the larger and more angular bone of Balanerpeton. The palate (roof of the mouth) was closed up by bone, lacking the large interpterygoid vacuities characteristic of temnospondyls. The palate was covered with striations and tiny tooth-like structures known as denticles. The broad front portion of the palate also possessed evidence for large fangs on the vomer and palatine bones.
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The front teeth in the lower jaw were larger than those of the upper jaw. The front edges of the crowns bore eight denticles (serrations), and the back edge bore nine to eleven. The teeth in the back of the upper (maxilla) and lower jaw were triangular in side view and compressed in front view. They had long roots that were oval in section, and the crowns had a marked at their bases.
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The dental formula for Dorudon atrox is . Typical for cetaceans, the upper incisors are aligned with the cheek teeth, and, except the small I1, separated by large diastemata containing pits into which the lower incisors fit. The upper incisors are simple conical teeth with a single root, lacking accessory denticles, and difficult to distinguish from lower incisors. The upper incisors are missing in most specimens and are only known from two specimens.
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The lateral teeth are wide, broad as long, the reflected portion almost as large as the whole base of attachment, and tricuspid, the inner cusp very small, the median cusp large and bluntly truncated, the outer cusp smaller than the median and bluntly pointed. The marginal teeth are subquadrate, wider than high, the apex reflected, obliquely produced and bearing five or more blunt, short denticles, of which the inner two are the largest.
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The skin is soft and covered by tiny, flattened dermal denticles (scales), lending a velvety texture. Each denticle has three horizontal ridges that lead to teeth on the posterior margin. The dorsal coloration is a medium to dark gray or slate, extending to the bases of the pectoral fins. The underside is white; adults in the Southern Hemisphere often have dark coloring under the head and dusky blotches scattered over the belly.
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The thread-like tail lacks dorsal or caudal fins, though there are low ridges along its length above and below. Its length is about equal to the distance between the snout tip and the vent, distinguishing this species from other butterfly rays that have shorter tails. Sometimes there is a small stinging spine (very rarely two) on the upper surface of the tail near the base. The skin is devoid of dermal denticles.
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Front teeth are small and peg-like with an ovular cross section and were most likely used for grabbing food. In some species, the last premaxillary tooth was enlarged and canine-like. Back teeth are small and triangular with denticles on the front and back of the crown, used for mouth processing. In species in which the dentary has been found, mandibular teeth are similar in size and shape to those in the upper jaw.
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The bighead spurdog (Squalus bucephalus) is a rare and little-known species of dogfish shark in the family Squalidae. It is found in deep water south of New Caledonia, and over the Norfolk Ridge. Reaching at least in length, this stocky shark is brown above and light below, with a broad head and two dorsal fins with long spines. It is the only member of its genus with both one- and three-pointed dermal denticles.
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Species of Hindeodus are divided into two groups based on the morphology of the posterior portion of the elements. Species such as H.parvus and H.eurypyge grow posteriorly and look rectangular from a lateral perspective. Elements grow by the addition of new denticles to the posterior margin. After one denticle fully grows, a bulge begins to form on the lower posterior margin of the element, and gradually grows upward until the denticle fully develops.
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These elements tend to preferentially grow on the posterior portion of the element leading to a more sloped shape. Hindeodus is part of a large clade Prioniodontida (otherwise known as "complex conodonts") which has two major orders of conodonts, Prioniodinina and Ozarkodinina. Hindeodus is part of Ozarkodinina in the family Anchignathodontidae. The synapomorphies that define the clade Prioniodontida is the presence of a P elements with an inner lateral process and peg-like denticles.
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G. gracilis holotype The species was described from a pair of wingless females, assumed to be workers. There is a covering of tapered setae along the upper surface of the clypeus, and the front corners of the clypeus cover the bases of the mandibles. There is a row of over 20 denticles along the front edge of the clypeus. Small ocelli are positioned just above and between the rear margins of the compound eyes.
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The snout is moderately long and bulbous, and there are no labial furrows at the corners of the mouth. The teeth are moderately large with a single, narrow cusp. There are 19-24 teeth in the upper jaw and 20-24 teeth in the lower jaw; their shapes are similar in both jaws. There are large and small dermal denticles, with the smaller ones more numerous and interspersed amongst the larger ones.
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The smooth lanternshark or slender lanternshark (Etmopterus pusillus) is a species of dogfish shark in the family Etmopteridae, found widely in the Atlantic and Pacific Oceans. It inhabits benthic environments at a depth of , and pelagic environments at a depth of . The smooth lanternshark forms a species group with the larger blurred lanternshark (E. bigelowi), both of which are distinguished from other members of their family by small, irregularly arranged dermal denticles with a truncated shape.
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The first dorsal fin is moderately tall and falcate (sickle-like) in shape, with a rounded tip. The pectoral and pelvic fins are not falcate, rather having nearly straight rear margins. The anal fin is larger than the second dorsal fin, with long free rear tip and a strong notch in the rear margin. The dermal denticles are densely packed, each with 5-7 horizontal ridges (3 in juveniles) leading to a W-shaped rear margin.
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Electric rays have a rounded pectoral disc with two moderately large rounded-angular (not pointed or hooked) dorsal fins (reduced in some Narcinidae), and a stout muscular tail with a well-developed caudal fin. The body is thick and flabby, with soft loose skin with no dermal denticles or thorns. A pair of kidney-shaped electric organs are at the base of the pectoral fins. The snout is broad, large in the Narcinidae, but reduced in all other families.
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Both dorsal fins have very long free rear tips, and there is a subtle midline ridge between them. A prominent notch is present on the caudal peduncle at the dorsal origin of the caudal fin. The caudal fin has a well-developed lower lobe and a longer upper lobe with a ventral notch near the tip. The skin is covered by overlapping, oval-shaped dermal denticles; each denticle has three horizontal ridges leading to marginal teeth.
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The caudal peduncle has a deep crescent-shaped notch at the upper caudal fin origin. The asymmetrical caudal fin has a well-developed lower lobe and a longer upper lobe with a notch in the trailing margin near the tip. The skin is covered by overlapping dermal denticles; each denticle has three horizontal ridges leading to three (rarely five) marginal teeth. This species is gray above and white below, with an obvious pale stripe on the flanks.
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The two workers known have body lengths between , and heads that range between . The coloration seen on specimen DO-I 980 indicates black tones on the ridges and rear corners of the head along with the lamellae edges which border the pronotum. The front edges of the lamellae on the gaster are rust colored and semi-transparent. The head is almost square in outline, with broadly curved rear corners and a concave rear margin sporting two denticles.
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Along with marine applications, the aerospace industry can also benefit from these biomimetic designs. Parametric modeling has been done on shark denticles with a wide range of design variations such as low and high-profile vortex generators. These biomimetic models were designed and analyzed to see the effects of applying the denticle-like structures to the wings of various airplanes. During the simulation, it was noted that the sample altered how the low and high angles of attack reacted.
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The pelvic fins are triangular and larger than the anal fin, which has a deep notch in the trailing margin. A crescent-shaped notch is present on the caudal peduncle at the upper caudal fin origin. The caudal fin is asymmetrical, with a well-developed lower lobe and a longer upper lobe with a ventral notch near the tip. The dermal denticles are slightly overlapping and bear three prominent horizontal ridges leading to three or five marginal teeth.
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Most of the entire latter half of its tail supports a distinctively long, slender, leaf-shaped caudal fin. Its coloration is dark above and white below, and its skin is almost completely covered by tiny dermal denticles. Preying on crustaceans, cephalopods, and bony fishes, the deepwater stingray may hunt both on the sea floor and well above it in open water. It is probably aplacental viviparous, with the mother supplying her gestating young with histotroph ("uterine milk").
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A slender, black shark reaching in length, the viper dogfish can be recognized by its narrow, triangular jaws and well-spaced, fang-like teeth. It also has two spined dorsal fins, dermal denticles with faceted crowns, and numerous light-emitting photophores concentrated on its ventral surface. Feeding mainly on bony fishes, the viper dogfish captures prey by protruding its jaws and impaling them with its teeth. Its impressive gape allows it to swallow relatively large fish whole.
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Its body is egg-shaped, with its maximum height in its body's second quarter. Its dorsal margin is quite arched, with its posteroventral angle denticles being very small. It carries about 35 to 40 ventral setae, with its posterior setae being longer than in cogenerate species. Its head has a low keel, the distance between its eye and the margin of its keel being equal to its eye diameter, which measures 1.5–2 times more than the ocellus.
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Its postabdomen is moderately long and narrow, somewhat narrowing distally, its length being about 3.2 times its height. Its preanal angle is well defined, while its postanal angle is not so. The postanal margin of the postabdomen is provided with 8 to 9 groups of tiny denticles. It also counts with 12–14 lateral fascicles of long setules, which in distalmost fascicles the length of its setules exceed the width of the base of its postabdominal claw.
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Myanmyrma has very long mandibles that near the same length as the head. Each mandible has only two large teeth, one blunt subapical, one sharp apical and the right mandible is notably longer than the left. The clypeus is modified with two large lobes, one on each genal margin and having about fourteen denticles. Occeli are not detectable on the holotype, but the presence of them was not ruled out due to the position of the specimen.
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The following twelve were leaf- or spade-shaped, with fine crenelations on the trailing edge. These are similar to the teeth of some prosauropods and early ornithischians, but differ in important features. For example, the teeth lacked the swellings and ridges seen in the teeth of early ornithischians like Lesothosaurus, and the coarse denticles (smaller points) of leaf-shaped ornithischian and prosauropod teeth in general. Phyllodontosuchus also lacked a predentary as found in all known ornithischians.
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The closest relative of Lasiognathus is Thaumatichthys, which also has enlarged and hinged premaxillaries, escal denticles, and a branched upper operculum. However, there are significant differences between those two taxa as well, which includes characters that Lasiognathus shares with the oneirodids not found in Thaumatichthys. Bertelsen and Struhsaker (1977) noted that, given the undefined cladistics of the Oneirodidae, it was somewhat subjective whether Lasiognathus and Thaumatichthys were placed in their own family, in separate families, or in the Oneirodidae.
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There is also a postparietal bone, which is small and triangular. At the back of the skull, the posttemporal foramen is large relative to the skull's width. Also unlike Turfanosuchus and Yonghesuchus, Gracilisuchus has four teeth in the premaxilla instead of five, like Prestosuchus, Saurosuchus, Fasolasuchus, Batrachotomus, the Rauisuchidae, and the Crocodylomorpha. There is no cutting edge, or carina, at the front of the premaxillary teeth, and they lack serrated denticles on either the front or rear edges.
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The tail spine averages long with 90 serrations in males, and long with 87 serrations in females. Behind the spine, there is a low dorsal keel and a ventral fin fold measuring less than half as long as the disc width. Mature individuals have a row of 2-10 tubercles on the snout tip, 3-5 tubercles on the back, and 1-8 tubercles before the spine. The tail is covered by dermal denticles towards the tip.
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The front edge of the propodium has a collar like ring of hairs. The gaster is attached to the petiole with a broad connection on the second metasomal segment, while the petiole is generally stalk shaped. A sting is present and partly extended from the gaster tip. C. janovitzi mandibles, labrum, and denticles Similar to the C. janovitzi gyne is the Camelomecia species gyne described, but the mandibles are slightly more elongated then the holotype gyne.
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The species' tail is extremely long and slender for a skate and is completely absent of dorsal fins; these factors make the species easily distinguishable from other skate species in the area. It has a large number of denticles on its dorsal disc, completely covering it. Male specimens have thorns on their anterior disk as adults and females have them in the middle of their tail and disc. In addition, males adults have claspers, which are thin and long.
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Two small, closely spaced dorsal fins are located near the tip of the tail. Adults have small dermal denticles and usually no midline thorns, though there are strong spines on the dorsal surfaces of the head, shoulders, and tail. Males tend to have fewer spines than females. The coloration of the little skate ranges from grayish to uniform or variable shades of brown above, becoming lighter towards the edges of the disk, and white or gray below.
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The pelvic fins are small with rounded rear margins; males have short, stout claspers. The slender, flattened tail measures 82-90% as long as the disc, and terminates in a low, leaf-shaped caudal fin; there is a prominent skin fold running along each side. A very thin, serrated stinging spine is positioned atop the tail about halfway along its length; immediate in front is a long, low dorsal fin. The skin entirely lacks dermal denticles.
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Newborn pincushion rays have smooth skin; older fish develop numerous large, thorny dermal denticles over the upper surface of the body and tail. The dorsal coloration is uniform dark brown or gray-brown, and the tail is nearly black past the base. The underside is white with a broad dark edge around the margin of the disk. This species grows to a large size; Smith recorded specimens measuring across and long, which required four men to lift.
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The only known specimen of the New Ireland stingaree is a juvenile male collected by René Primevère Lesson and Prosper Garnot, during the 1822-25 expedition of the French frigate La Coquille. It was first referenced as Urolophus armatus by Achille Valenciennes, and furnished with a description by Johannes Müller and Jakob Henle (who are thus considered the species authorities) in their 1838-41 Systematische Beschreibung der Plagiostomen. Its specific epithet means "armed" in Latin, referring to its denticles.
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These include bone beds, and the area is a declared important educational resource for the study of vertebrate palaeontology. Most important are the plates of Cyathaspis banksi. The remains of primitive fish include thelodont denticles and acanthodian fragments.Natural England SSSI information on the citation Inspections by Natural England in 2009 report only acceptable change due to the natural processes of estuarine muds, and no establishment of vegetation; this is controlled due to the natural process of tidal scour.
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L. dynatis had smaller teeth, but had more of them compared to L. paludis. The ridge of the pterygoid flange of L. dynatis was narrow compared to L. paludis, possessing smaller teeth and denticles. The supraoccipital of L. paludis consisted of a single element, while it consisted of two paired elements in L. dynatis. The scapulocoracoid of L. dynatis was shorter and wider than the scapulocoracoid of L. paludis, while also being thinner and less convex.
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This trochal band is also found in sessilid peritrichs, where it is ciliated only during the swarmer (telotroch) phase of the cell's life, during which the organism can swim freely. In mobilid ciliates, the trochal band is a permanent feature of the cell. Mobilids possess a conspicuous "adhesive disk" at the aboral (posterior) pole, enabling the organism to attach itself temporarily to its host organism. This disk is radially symmetrical and composed of interlocking curved denticles and associated fibres.
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In most individuals the skin is completely smooth, which distinguishes this species from the pitted stingray (which has spines on the back and tail); in the largest known female specimen, tiny denticles are scattered atop the disk around the tail base. The dorsal coloration is yellowish to greenish brown above, becoming more reddish towards the disk margins. The underside is white with dark fin margins, while the tail fin folds are black. This species attains a width of .
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Extensive article on the role of menhaden in the ecosystem and possible results of overfishing. In addition to these bony fish, four types of cartilaginous fishes are also filter feeders. The whale shark sucks in a mouthful of water, closes its mouth and expels the water through its gills. During the slight delay between closing the mouth and opening the gill flaps, plankton is trapped against the dermal denticles which line its gill plates and pharynx.
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The pelvic fins are rounded and almost as large as the pectoral fins. The anal fin is less than half the size of the dorsal fins and is positioned very close to the base of the long, low caudal fin. The caudal fin comprises about a quarter of the total length, with no ventral lobe and a strong ventral notch near the tip of the upper lobe. The dermal denticles are large, giving the skin a rough texture.
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The second dorsal fin is larger than, and originates ahead of, the anal fin; both these fins are positioned very close to the caudal fin. The caudal fin has a long upper lobe with a ventral notch near the tip, and an indistinct lower lobe. The dermal denticles are shaped like arrowheads with a central ridge, and are sparsely distributed on the skin. This species is typically plain dark brown in color, darkening at the fin margins.
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There are rounded rectangular carinae surrounding each of the oval eyes, and the ocelli are placed equidistantly from each other on the flat area of the head. There are scattered short setae on both gena and the clypeus. The lower margin of the clypeus has 20 denticles and a row of eight to ten longer setae that point toward the mandibles. The mesosoma is smooth with little sculpturing other than the protruding spiracles and the deep distinct metanotal groove.
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There are curved and spiral like carinae which start at the antennae sockets and curve around to the bottom margins of the compound eyes. The trapazoid shaped clypeus has raised areas on both edges and in a mound at its middle. Sparse setae are found on upper surface of the clypeus and approximately 25 denticles line the lower edge. The head is connected to the pronotum with a broad attachment area, while the petiole is a node shape.
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All of the eyes are white in color, except for the anterior median eyes which are black. The fang appendages (chelicerae) are strong and vertically oriented. They possess large forward facing teeth on the cheliceral groove, three in females and four in males, evenly spaced from each other. Very small backward facing teeth (denticles) are also present in a row on the basal half of the cheliceral groove, five in females and three to four in males.
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The skin is thick and covered by well- calcified dermal denticles. The coloration of the draughtsboard shark gives it its common name: it is golden to brown above and light below, with up to 11 dark brown, irregular dorsal "saddles" that alternate with blotches on its flanks to form a checkerboard pattern. Also distinctive is the saddle between its spiracles, which is stretched out and swept back on each side to form a bar over the gill slits.
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Though several fossilised instars of Jaekelopterus howelli are known, the fragmentary and incomplete status of the specimens makes it difficult to study its ontogeny in detail. Despite this, there are some noticeable changes occurring in the chelicerae, telson and metastoma. Four of the J. howelli specimens studied by Lamsdell and Selden (2013) preserve the chelicerae in enough detail to allow for study of the denticles. Two of these chelicerae were assumed to come from juveniles and two were assumed to be from adults.
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The sublingua, or "under-tongue", is a secondary tongue located below the primary tongue in tarsiers, lemuriform primates, and some other mammals. This structure does not have taste buds or salivary glands. In lemuriforms, the sublingua is relatively large and its front edge is usually lined with keratinized serrations (sometimes called "denticles"). The serrated edges of a strepsirrhine sublingua are part of the plicae fimbriatae, while the plica sublingualis, which attaches the sublingua and tongue to the floor of the mouth, is small.
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The arrangement of teeth (denticles) on the radular ribbon varies considerably from one group to another. In most of the more ancient lineages of gastropods, the radula is used to graze, by scraping diatoms and other microscopic algae off rock surfaces and other substrates. Predatory marine snails such as the Naticidae use the radula plus an acidic secretion to bore through the shell of other molluscs. Other predatory marine snails, such as the Conidae, use a specialized radular tooth as a poisoned harpoon.
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Body moderately stout and compressed, preoral snout moderately long, about half of distance from mouth to pectoral origins; mouth narrowly arched, nearly half as high as wide. Second dorsal fin somewhat larger than first; pectoral apices when laid back ending about opposite to first dorsal spine origin. Caudal peduncle moderately long, distance from second dorsal insertion to upper caudal origin about as long as distance from eye to third gill slits. Lateral trunk denticles close-set, conical and with hooked cusps.
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Atherion elymus has an elongated, compressed bosy with a small month in which the upper jaw does not extend as far as the front egde of the eye. The head has a number of rows of denticles or small spines. Its anus sits immediately in front of the origin of the anal fin. The colouration is greenish gray on the back and whitish on the underside with a wide silvery band along the flanks which extends to the caudal fin.
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Early Eocene fossil stingray Heliobatis radians Batoids belong to the ancient lineage of cartilaginous fishes. Fossil denticles (tooth-like scales in the skin) resembling those of today's chondrichthyans date at least as far back as the Ordovician, with the oldest unambiguous fossils of cartilaginous fish dating from the middle Devonian. A clade within this diverse family, the Neoselachii, emerged by the Triassic, with the best-understood neoselachian fossils dating from the Jurassic. The oldest confirmed ray is Antiquaobatis, from the Pliensbachian of Germany.
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The black dogfish has a stout, dark brown body and large green eyes; this specimen has light patches where its dermal denticles have rubbed off from handling. Adult black dogfish typically measure in length and can reach , making it the largest member of its family. Females attain a larger ultimate size than males. The shark has a rather stocky and laterally compressed body, with a moderately long, thick, and flattened snout that forms a very broad arch at the front.
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Arranged in arcs around the periphery are the statutory inscriptions "UNITED•STATES•OF•AMERICA, E•PLURIBUS•UNUM, LIBERTY" and "IN• GOD•WE•TRUST". The date 1938 and value "HALF•DOLLAR" appear at the bottom in two lines. The New Rochelle half dollar is the last U.S. coin to have denticles along the rim, a feature that had been previously eliminated on the circulating coinage. It was also the last new- design commemorative to be struck by the U.S. until 1946.
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Pescetarianism (provided the fish is ruled kosher) conforms to Jewish dietary laws, as kosher fish is "pareve"—neither "milk" nor "meat". In essence, aquatic animals such as mammals like dolphins and whales are not kosher, nor are cartilaginous fish such as sharks and rays, since they all have dermal denticles and not bony- fish scales. In 2015, members of the Liberal Judaism synagogue in Manchester founded The Pescetarian Society, citing pescetarianism as originally a Jewish diet, and pescetarianism as a form of vegetarianism.
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The caudal fin is short and broad, with an indistinct lower lobe and a ventral notch near the tip of the upper lobe. The very thick skin is covered by well-calcified dermal denticles. Each denticle has an arrowhead-shaped crown with three posterior points, mounted on a short stalk. The background color of the leopard catshark ranges from off-white to glossy jet black above and white to almost black below, sometimes with an abrupt transition between the two.
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These opuntioid plants grow in low opuntioid cushions, consisting of rather ovoid or slightly clavate segments, from 1 up to 25 cm long, tuberculate, not ribbed, glabrous. Spines are strong, very prickly and dangerous, covered on their margins by fine denticles, with epidermal tunica (sheath) at the apex only. Flower generally yellow, few species have pink to deep magenta flower. Fruit narrowly obconic to ellipsoid, fleshy at first but soon drying, yellow to brownish, often stinky, generally full of glochids and spiny.
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The green lanternshark (Etmopterus virens) is a species of dogfish shark in the family Etmopteridae, found in the western central Atlantic Ocean. This species usually occurs on the upper continental slope below a depth of . Reaching in length, the green lanternshark has a slender body with a long, thin tail and low, conical dermal denticles on its flanks. It is dark brown or gray with ventral black coloration, which contain light-emitting photophores that may serve a cryptic and/or social function.
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The roughnose stingray (Pastinachus solocirostris) is a little-known species of stingray in the family Dasyatidae, generally found in shallow, estuarine waters associated with mangroves off Borneo, Sumatra, and possibly Java. Growing to across, this species has a rhomboid pectoral fin disc and a whip- like tail with a ventral fin fold. It is characterized by its pointed snout, which is covered by dermal denticles. Reproduction is aplacental viviparous, with females possibly bearing as few as one pup at a time.
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The Hebrew volute has a pale ivory colored body, ornamented by numerous irregular and intertwined thin dark-red to brown colored lines, and several small spots of the same color along the sides of the foot. Some of the most distinct external features are its very large foot, and a long siphon. This species presents a Steoglossan type radula, composed of a single row of rachidian or central teeth. Each one of these teeth exhibits several smaller acute denticles or cusps.
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The skin is devoid of dermal denticles. The masked stingaree has an ochre to gray dorsal coloration with two large, distinctive dark blotches, one forming a "mask" around the eyes and the other at the center of the disc; these blotches may be connected by thin lines along the midline and on either side. The underside is white, becoming darker at the fin margins. The dorsal and caudal fins are black in young rays, and fade to gray in adults.
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At the end of the tail is a very short, deep, leaf-shaped caudal fin. The skin is entirely devoid of dermal denticles. The crossback stingaree is grayish to yellowish brown above with a pattern of dark markings, including a stripe running along the midline and crossed by three transverse bars: one near the eyes, one over the gill region, and one over the center of the disc. The pattern is strongest in rays from the southern portion of its range.
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Bones of the snout are more loosely articulated with each other than the bones of the posterior skull. The are long, with very deep as in other iguanodontians. Anteriorly, the premaxillae flare gently laterally into a rugose surface for a beak, like other iguanodontians, although dissimilar from Iguanodon and similar to hadrosaurids the nares are entirely visible from above. Neither premaxilla bears any teeth, although the very anterior tip has "pseudo-teeth" formed by multiple denticles on the margin of the bone.
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Within the gastropods, the radula is used in feeding by both herbivorous and carnivorous snails and slugs. The arrangement of teeth (also known as denticles) on the radula ribbon varies considerably from one group to another as shown in the diagram on the left. Predatory marine snails such as the Naticidae use the radula plus an acidic secretion to bore through the shell of other molluscs. Other predatory marine snails, such as the Conidae, use a specialized radula tooth as a poisoned harpoon.
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Like the more posterior premolars, it is buccolingually compressed and double-rooted. It has a dominant central protocone flanked by denticles that decrease in size mesially and distally, resulting in a tooth with a triangular profile. P3 is similar to but slightly smaller than P2, except that it has a projection on the lingual side which is the remnant of a third root. In P4, smaller than P2–3, the larger distal root is formed by the fusion of two roots.
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The curvature and length of the holotype tooth and the length of its hindmost cutting edge (carina) indicates it was in the front of the jaw. Estimated size of Dromaeosauroides, and possible placement of the two known teeth The tooth is recurved with a backward bend, and is oval in cross-section. Its front and back cutting edges are finely serrated, extending two-thirds down each edge. There are six denticles per millimeter (0.04 in), and each denticle is square and chiseled.
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It has no anal fin, but two dorsal fins approximately equal in size. The first dorsal fin originates about halfway from the tip of the snout to the tip of the caudal fin, the origin of the second dorsal fin is posterior to the tips of the pelvic fins. It has large pectoral fins, that's inner margins curve inward toward the base of the fins. There are dermal denticles on the dorsal surface of the body with very little overlapping.
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The Niger stingray or smooth freshwater stingray, Dasyatis garouaensis, is a species of stingray in the family Dasyatidae, native to rivers in Nigeria and Cameroon. Attaining a width of , this species can be distinguished by its thin, almost circular pectoral fin disk, slightly projecting snout tip, and mostly smooth skin with small or absent dermal denticles. The Niger stingray feeds on aquatic insect larvae and is ovoviviparous. The long stinging spine on the tail of this ray can inflict a painful wound.
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The marbled whipray (Himantura oxyrhyncha) is a little-known species of stingray in the family Dasyatidae, native to several freshwater rivers in Southeast Asia. This species has an oval pectoral fin disc with an elongated, pointed snout and a very long, whip-like tail without fin folds. It is characterized by numerous heart-shaped dermal denticles and tubercles on its upper surface, as well as a reticulated pattern of brown blotches on a light background. The maximum recorded disc width is .
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There are two small dorsal fins, both with rounded to angular apices; the first is slightly smaller than the second, and its position varies from over to behind the pelvic fins. The caudal fin is triangular with rounded corners, and is roughly symmetrical above and below. The skin is soft and entirely devoid of dermal denticles. The dorsal coloration of the ocellated electric ray is extremely variable, with the only constant being the large ocellus ("eyespot") in the middle of the back.
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At the sutures, and in the middle of the body whorl (in some specimens also on the upper whorls), there is a very pale ochraceous banding, the nodules of the ribs still retaining their white lustre. In other specimens the first three or four whorls remain quite colourless. The aperture is oblong. The sinus is sutural, oblquely extending over the outer lip, which is much incrassate within with seven prominent denticles, these being provided with three also of lesser size.
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Teeth of Kwanasaurus have been found both as isolated material and within maxillae and dentaries. Isolated teeth are leaf-shaped, with coarse denticles, slightly flattened sides, and crown tips more than halfway towards the rear of the tooth. The lingual (tongue) side of the tooth has a thick vertical ridge covered in striations. Sacisaurus, Eucoelophysis, and possibly Technosaurus are the only other silesaurids known to possess similar teeth, although leaf-shaped teeth are also common in various other herbivorous archosaurs.
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The caudal fin has a strong lower lobe and a long, narrow upper lobe with a ventral notch near the tip. The dermal denticles are small, oval, and overlapping, bearing three horizontal ridges leading to marginal teeth. This shark is steel-gray above and white below; the color transition is sharp, located well below the eye, and becomes jagged on the sides of the trunk. The anal and caudal fins become dusky or black towards the trailing margins and tips.
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Sharklet material was developed by Dr. Anthony Brennan, materials science and engineering professor at University of Florida, while trying to improve antifouling technology for ships and submarines at Pearl Harbor. Brennan realized that sharks do not experience fouling. He observed that shark skin denticles are arranged in a distinct diamond pattern with millions of tiny ribs. The width-to-height ratio of shark denticle riblets corresponded to his mathematical model for the texture of a material that would discourage microorganisms from settling.
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Early Eocene fossil stingray Heliobatis radians Skates belong to the ancient lineage of cartilaginous fishes. Fossil denticles (tooth-like scales in the skin) resembling that of today's chondrichthyans date at least as far back as the Ordovician, with the oldest unambiguous fossils of cartilaginous fish dating from the middle Devonian. A clade within this diverse family, the Neoselachii, emerged by the Triassic, with the best-understood neoselachian fossils dating from the Jurassic. This clade is represented today by sharks, sawfish, rays and skates.
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In front of the clypeus, the bases of the long straight mandibles are placed close together. On the masticatory margin there are no denticles, with possibly three teeth present at the tip end of each mandible, though only two are visible. The thorax is slightly elongated, with a mesoscutum that is a little wider than long and attaching with no overhang of the sclerites to the propodeum. The petiole is rounded and narrow, without a spine on the upper surface.
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Although fragmentary, the fossils of this animal have enough to differentiate it from other similar plesiosaurs. Makhaira must have measured about long, and like its other relatives, must have had a compact body with four large paddle-like limbs. The skull was elongated, particularly in the rostral area, with several sharp teeth. The characteristics of these teeth are unique, they are triangular in cross view and had carinae or grooves with denticles at the edges, which possessed a height greater than its width.
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The describing authors established some diagnostic traits. In the depression for a skull opening, the fenestra antorbitalis, to the front a second opening is present, a fenestra maxillaris, that occupies much of the front part of this depression. The teeth in the maxilla only on their rear edges have denticles which are very small and directed towards the point of the teeth. The neck vertebrae are mildly opisthocoelous: with centra that are convex in front and concave at the rear.
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Teeth on the vomer bones form a second parallel row on the palate that is not as extensive as the marginal tooth row. At about in diameter, these teeth are smaller than the marginal teeth. The rest of the palate has subtle pustular ornamentation at a finer scale than on the skull roof. This is a unique condition among early tetrapods, many of which have more extensive ornamentation on the palate including bony denticles, additional tooth rows, and palatal tusks.
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Workers of Leptomyrmex can be easily recognized by elongate antennal scapes which surpass the posterior margin of the head by more than one half their length, a medially notched hypostoma, mandibles with 7–15 teeth and 5–12 denticles, and a laterally located anterior tentorial pit. Queens are known from only seven species. All known macro-Leptomyrmex queens are wingless (ergatoid). They can be differentiated from workers by the presence of ocelli and their larger size, including enlarged mesosoma and gaster.
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The pelvic fins are low and angular, and there is no anal fin. The caudal fin is short and broad, with a well-developed lower lobe and a ventral notch near the tip of the upper lobe. The skin is covered by many widely spaced, small blocky denticles not arranged in regular rows, giving it a smooth appearance. The coloration is a uniform dark brown, with a faint black mark over the bases of the pelvic fins extending both forward and backward on the flank.
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The pectoral fins are moderately large; the dorsal, pelvic, and anal fins are of similar size. The broad caudal fin comprises a fifth of the total length; the upper lobe has a deep ventral notch near the tip and the lower lobe is virtually absent. The skin is thick and covered by well-calcified, leaf-shaped dermal denticles. The coloration is brown above and white below; the brown shyshark is usually plain while the other species have varying patterns of darker "saddles" and white spots.
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A crescent-shaped notch is present on the caudal peduncle just before the upper caudal fin origin. The caudal fin is asymmetrical, with a strong lower lobe and a longer upper lobe with a ventral notch near the tip. The roughly diamond-shaped dermal denticles are placed closely together and slightly overlapping; each bears five to seven (three in juveniles) horizontal ridges leading to marginal teeth. The Australian blacktip shark is bronze above (gray after death) and whitish below, with a pale stripe on the flanks.
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The pelvic fins are small with pointed to narrowly rounded tips, and the anal fin has a deep notch in its trailing margin. The asymmetrical caudal fin has a strong lower lobe and a longer upper lobe with a ventral notch near the tip. The dermal denticles mostly do not overlap; each has three to five horizontal ridges leading to posterior teeth, with the central one the longest. This shark is plain gray to slate above and whitish below, with a faint lighter stripe on the flanks.
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However, in recent work one such species, Tungussogyriinus bergi has been further analyzed and shown to share clear synapomorphies with branchiosaurids including the Y-shaped palatine resulting in a gap between ectopterygoid and maxilla as well as brush-like branchial denticles. T. bergi differs from all other branchiosaurids in two autapomorphies: elongated process of ilium and tricuspid dentition. Thus, Tungussgyrinus is thought to represent a clade that is the closest relative to all other branchiosaurids and two new subfamilies, Tungussogyrininae and Branchiosaurinae fall under Branchiosauridae.Werneburg, R. 2009.
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One or two relatively large, serrated stinging spines are placed atop the tail about halfway along its length. Some species have a small dorsal fin immediately before the spine, and/or lateral skin folds running along either side of the tail. All species lack dermal denticles (except for the New Ireland stingaree, U. armatus). Stingarees are generally shades of yellow, green, brown or gray above and pale below; some species are plain, while others are adorned with spots, rings, blotches, lines, or more complex patterns.
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The slender caudal fin originates a short distance behind the sting; it is symmetrical above and below, and terminates in a rounded leaf-like shape. The skin is densely covered by fine dermal denticles, that become sparse to absent on the pelvic fins, towards the ventral disc margin, and around the mouth. The deepwater stingray is purplish brown to blackish above; some rays also have irregular darker blotches and spots. The underside is white, with a narrow dark border along the lateral disc margins.
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The columella, weakly concave in its upper part, is furrowed in its entire length by numerous folds, very distinct but rather thin, which run along the edge in its width and In the interior. The outer lip, seen from the front, offers a fairly regular semi-oval profile. Seen in the plane of the aperture, it is flexibly arched. Thickened on the last rib, it presents a sharp lip below which comes a large number of small well-marked folds, which appear as denticles.
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Dahlella may reach a length of from the base of the rostrum to the end of the abdomen. Much of the animal is covered by a large, hinged carapace. Dahlella can be distinguished from other animals in the same family by the presence of a row of denticles (small teeth) on the eyestalks, which it is believed are used to scrape surfaces for food. A similar character is found in Paranebalia (Paranebaliidae), but the form of the eyestalk is very different in the two taxa.
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The uniquely foldable teeth indicate that Andersonerpeton is an aistopod, as these teeth are also seen in Coloraderpeton and Oestocephalus, but no other tetrapods until the appearance of snakes in the Cretaceous period. In addition, the mandible was smooth and wide, similar to that of most aistopods. However, in many other features the jaw of Andersonerpeton closely resembles early tetrapod relatives such as Elginerpeton. These include the arrangement of teeth and denticles on the parasympheseal and coronoid bones, as well as labyrinthine marginal teeth.
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The longsnout dogfish (Deania quadrispinosa) is a little-known deepwater dogfish, found in the Atlantic and Indian Oceans from Namibia to Mozambique and in the South Pacific off southern Australia and New Zealand. The longsnout dogfish has an extremely long, angular snout, no anal fin, dorsal fins of similar size with the first placed high on the back and the second having a longer rear free tip, and pitchfork-shaped dermal denticles. It is dark brown and grows to about 114 cm. Reproduction is ovoviviparous.
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The of the upper jaw were lined with 15 blade-like teeth on each side in the holotype. The first eight of these teeth were very long and robust, but from the ninth tooth onward they gradually decrease in size. As typical for theropods, they featured finely edges, which in the holotype contained some 10 denticles per . Specimen MWC 1 merely showed 11 to 12, and specimen UMNH VP 5278 12 teeth in each maxilla; the teeth were more robust and more recurved in the latter specimen.
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The basal segment of the antennae, the scape, is elongated, reaching back past the rear margin of the head. The males have a slightly rectangular heads that are wider than long, and dominated on each side by convex large compound eyes. The mandibles have large apical teeth and possibly small denticles, similar to males of the living species Zatania gibberosa. As in the workers, the antennae have elongated scapes that extend beyond the rear margin of the head and have short setae on them.
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The upper surface of the body and tail are roughened by tiny dermal denticles, which become larger towards the midline of the back and tail. In addition, one or two irregular rows of thorns are present along the dorsal midline from the head to the sting. The mangrove whipray is dark brown to gray above with many white dots and flecks, which become denser with increasing size. The dark coloration is due to a layer of mucus, without which the body is light orange-gray.
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The Chinese stingray, Hemitrygon sinensis, is a little-known species of stingray in the family Dasyatidae, found in the northwestern Pacific Ocean off the coasts of China and Korea. This species is characterized by a band of small dermal denticles running along the upper surface of its diamond-shaped pectoral fin disc, from the snout to the tail spine. It can grow to across and long. The Chinese stingray is taken incidentally in bottom trawls and is one of the three most commonly marketed stingrays in China.
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Although two female castes have not been collected together, they share characteristics unique to the Malagasy Meranoplus and indicate they belong to the same species: comparatively short scapes, widely set clypeal denticles, high oculomandibular indices (OMI), characters of sculpturation, and the striking orange bicoloration. The strong orange and black bicolored coloration of M. cryptomys is notable for its similarity to that of M. mayri. These two species overlap in range across the south and southeast of Madagascar, from Andohahela to Isalo. Males are unknown.
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The features that distinguish Biseridens from other anomodonts include the presence of heterodont dentition, or differentiated teeth rows in which different teeth have distinct morphology (ex. precanines, canines, molars, etc.), small toothlike projections, or denticles, located on the palatine and pterygoid, articulation between the opisthotic bone and the tabular bones on the posterior surface of the skull, the absence of the mandibular foramen on the lower jaw, and a pterygoid in which the transverse flange of the pterygoid has a laterally extending process but lacks posterior ramus.
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There are several diagnostic features that characterize this specimen as a Biseridens. Related to its heterodont dentition, Biseridens is distinct from other anomodonts because of a differentiated tooth row that includes two rows of teeth on both the jaws, precanine teeth on the dentary and premaxilla, and a broad spread of teeth on the pterygoid and palatine. There are also denticles on the vomer, palatine, and pterygoid. The postcanies possess oval cross sections and have grinding surfaces, and the canines have a basal diameter of 10mm.
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The skin is completely devoid of dermal denticles. The western shovelnose stingaree is grayish to ochre to dark brown in color above, becoming dusky to black on the caudal fin; some rays also exhibit an irregular scattering of lighter and darker spots. The underside is white to beige, occasionally with a wide, dark brown band and blotches along the margins of the disc and tail, which is most obvious in juveniles. This species has a maximum reported disc width of for males and for females.
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Some Pacific electric rays have dark spots on the upper surface. The Pacific electric ray has a soft, flabby body devoid of dermal denticles. It has an oval pectoral fin disc about 1.2 times as wide as long, with a nearly straight front margin and a pair of kidney-shaped electric organs visible beneath the skin. The eyes are small and followed by smooth- rimmed spiracles; the space from the spiracles to the snout tip is about 1.8 times the distance between the spiracles.
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The differences between their denticles also indicate they should be kept separate. According to Bonde, Dromaeosauroides is one of the oldest known dromaeosaurs in the world; older remains, for the most part, have only tentatively been referred to Dromaeosauridae. Dromaeosauroides was the first definite dromaeosaurid known from the Early Cretaceous of Europe, depending on the identity of Nuthetes from the Middle Purbeck formation of the United Kingdom (which may slightly predate the Jydegaard Formation). It is uncertain whether the juvenile holotype specimen of Nuthetes has dromaeosaurid characteristics.
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Both the front and back cutting edges are serrated, with two to four denticles per mm (0.04 in). The tooth also has longitudinal ridges on both sides, and the outermost enamel layer has a wrinkled texture in the regions between and without ridges. Among the oldest known spinosaurid fossils, Ostafrikasaurus may be of importance in understanding the evolutionary origins of spinosaurids and their anatomical adaptations. From comparisons with its later relatives, Ostafrikasaurus indicates that spinosaur teeth became more conical and lost their serrations throughout their evolution.
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Pristomyrmex tsujii varies in the abundance of the cephalic foveae, propodeal armament and petiolar node shape. In Koro (the type locality) and Gau the specimens exhibit a sparse scattering of foveae and punctures usually separated from each other by a distance exceeding their diameters. None of the Koro specimens are armed even with denticles and the petiolar node is relatively broad in profile with a weakly convex posterior face. The series from Taveuni has sparse fovea and the worker from Vanua Levu has moderate foveae.
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284 Earlier reconstructions, such as those by Marsh and Gilmore, were based on the skull of Theiophytalia and display an incorrect, more rectangular profile. The skull was in fact triangular with a pointed snout, equipped with a beak. Its teeth were more tightly packed in the jaw compared to other Morrison euornithopods. Museum curator John Foster describes them as having "thick median ridges on their lateral sides and denticles along their edges," these features were similar to, but "more fully developed" than those in Dryosaurus.
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The anal fin resembles the second dorsal fin but is larger and deeper. The caudal fin has a distinct lower lobe and a strong ventral notch near the tip of the upper lobe. The body is densely covered by small, overlapping arrowhead-shaped dermal denticles with a median ridge. Adults are light gray above, with numerous small dark spots interspersed with a series of larger dark saddles and blotches that contain small white spots, including a white-spotted blotch behind and another below each eye.
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Maxillae of Eolambia The crestless skull of Eolambia has a similar overall shape to those of Equijubus and Probactrosaurus. The front of the snout is highly roughened, being punctuated by many foramina (openings). At the tip of each premaxilla, there are two tooth-like structures known as denticles, which is also seen in its closest relative Protohadros. Further back, the rear portion of the lower branch of the premaxilla abruptly projects upwards, closing off the nostril at the rear as in Probactrosaurus, Protohadros, and other hadrosauroids.
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The shell is 17 to 27 mm in length, 10 to 16 mm in greatest diameter, with a low conical spire and an indistinct suture. The outer lip is thickened, and strongly reflected outward, with a sharp edge overhanging the exterior of the body whorl. The inside of the lip of the shell has 15-25 small irregular denticles, plus one very strong isolated denticle near its posterior end. The aperture is quite high for the genus, and it narrows both anteriorly and posteriorly.
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The most distinctive feature of sawfish is their saw-like rostrum with a row of whitish teeth (rostral teeth) on either side of it. The rostrum is an extension of the chondrocranium ("skull"), made of cartilage and covered in skin. The rostrum length is typically about one-quarter to one-third of the total length of the fish, but it varies depending on species, and sometimes with age and sex. The rostral teeth are not teeth in the traditional sense, but heavily modified dermal denticles.
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A 2009 study analyzed the differences in morphology, including color, meristic variation, spine, dermal denticles (tooth-like scales), and teeth of different populations. Two distinct species emerged: the smaller M. alfredi found in the Indo-Pacific and tropical east Atlantic, and the larger M. birostris found throughout tropical, subtropical and warm temperate oceans. The former is more coastal, while the latter is more ocean-going and migratory. A 2010 study on mantas around Japan confirmed the morphological and genetic differences between M. birostris and M. alfredi.
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In all other sauropods known from congruous remains this feature had been reduced already. On each side of the mandible there were 19 teeth – more than in all known sauropods, but fewer than in the prosauropod Plateosaurus. The teeth were lanceolate and furnished with coarse denticles; therewith they resemble those of prosauropods more than those of sauropods. However, the lingual side of the teeth already was slightly concave, possibly an initial state towards the strongly concave, spoon shaped teeth that were typical for sauropods.
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The radula, which is located inside the mouth, is a feeding structure that is unique to molluscs. Typically, it is a small, strong, ribbon-like structure that bears numerous complex rows of tiny teeth across it. In the Kerry slug, the radula is 8 mm (5/16 in) long and 2 mm (1/16 in) wide, and has 240 slightly curved, transverse rows of denticles; tiny teeth. Each row of teeth is composed of one median tooth and 10 lateral and marginal teeth on each side.
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Pair-rule genes are defined by the effect of a mutation in that gene, which causes the loss of the normal developmental pattern in alternating segments. Pair-rule genes were first described by Christiane Nüsslein-Volhard and Eric Wieschaus in 1980. They used a genetic screen to identify genes required for embryonic development in the fruit fly Drosophila melanogaster. In normal unmutated Drosophila, each segment produces bristles called denticles in a band arranged on the side of the segment closer to the head (the anterior).
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The first dorsal fin is triangular with a rounded apex, originating in front of the pelvic fin insertions. The second dorsal fin is only one-half to two- thirds as large as the first; the distance between the dorsal fins is less than the length of the first dorsal fin base. The stout tail comprises about one-third of the total length, terminating in a caudal fin shaped like an equilateral triangle with slightly convex margins. The skin is soft and completely devoid of dermal denticles (scales).
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Only a single row of denticles is present, and the vertexal margin (seen posterodorsally) is concave. The mesosoma is smooth and contains a single spine, fovea (a pit or depression in a structure) or carina (a keel- like elevation on the body-wall of an insect). The posterior portion of the propodeal surface is concave; it is high and strongly angled. All legs have flattened femurs (the largest region of an insect's leg) and tibiae, and the tibiae are carinated both anteriorly and posteriorly.
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The anuran larva or tadpole has a single central respiratory spiracle and mouthparts consisting of keratinous beaks and denticles. Panamanian golden frog (Atelopus zeteki). Frogs and toads are broadly classified into three suborders: Archaeobatrachia, which includes four families of primitive frogs; Mesobatrachia, which includes five families of more evolutionary intermediate frogs; and Neobatrachia, by far the largest group, which contains the remaining families of modern frogs, including most common species throughout the world. The suborder Neobatrachia is further divided into the two superfamilies Hyloidea and Ranoidea.
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Though this feature has since proved to be a misidentification, other features distinguishing the genus from its relatives have been identified, including a telson with a triangular shape and a different inclination of the denticles of the claws. The chelicerae and compound eyes of Jaekelopterus indicate it was active and powerful with high visual acuity, most likely an apex predator in the ecosystems of Early Devonian Euramerica. Although eurypterids such as Jaekelopterus are often called "sea scorpions", the strata in which Jaekelopterus fossils have been found suggest that it lived in fresh water environments.
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Though such growth in the denticles of pterygotids has been described in other genera, the massive elongation of the second intermediate denticle through ontogeny is unique to Jaekelopterus, particularly to J. howelli. The metastoma of Jaekelopterus also altered its dimensions as the animal matured. In J. rhenaniae, the relative width of the metastoma decreased through ontogeny. The metastoma in J. howelli is also broader in juveniles than in adults, although the length–width ratios measured in juveniles and adults were not as disparate as assumed, being 1.43 in juveniles and 1.46 in adults.
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The caudal peduncle has a deep notch on its upper surface at the caudal fin origin. The caudal fin is asymmetrical, with a well-developed lower lobe and a longer upper lobe with a notch in the trailing margin near its tip. The skin is covered by rather large dermal denticles, which become more tightly packed and overlapping with age; each denticle bears three to five horizontal ridges and five posterior teeth. This species is grey above and white below, with a faint pale band on the flanks.
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The asymmetrical caudal fin has a well-developed lower lobe and a longer, narrow upper lobe with a strong ventral notch near the tip. The dermal denticles are small and overlapping, each with three horizontal ridges leading to marginal teeth. This species is slate-gray above, darkening towards the tips of the dorsal fins and upper caudal fin lobe; some specimens have irregular rows of small, white blotches, which may be an artifact of handling. The underside is white, which extends onto the flanks as a vague pale band.
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They generally do not live in freshwater although there are a few known exceptions, such as the bull shark and the river shark, which can be found in both seawater and freshwater. Sharks have a covering of dermal denticles that protects their skin from damage and parasites in addition to improving their fluid dynamics. They have numerous sets of replaceable teeth. Well-known species such as the tiger shark, blue shark, great white shark, mako shark, thresher shark, and hammerhead shark are apex predators—organisms at the top of their underwater food chain.
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It consists of a row of 7 to 9 downward directed denticles along the front of the glabella, which interlocked with corresponding teeth on the pygidium, when the animal protected itself by enrolling. The eyes are small and raised above the cheeks but not connected to the glabella by an eye ridge. The facial sutures in genus Pliomera itself are gonatoparian, while in the genus Placoparia these are opisthoparian, and this is unlike all other pliomerids where facial sutures are proparian. The thorax may have between 12 and 18 segments.
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Ginglymostoma unami, also known as the Pacific nurse shark is a nurse sharks of the family Ginglymostomatidae. It is found in southeastern coast of Baja California, Mexico to Costa Rica including Gulf of California. This species differs from Ginglymostoma cirratum between posterior end of the second dorsal fin and the beginning of the caudal lobe, both being shorter; the new species also differs by the position of the insertion of the first dorsal fin with regard to the pelvic fins and in the form and number of keels on the dermal denticles and teeth morphology.
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The large aperture is oval in shape, with an elaborate peristome. The outer lip is flaring, thickened at a short distance from the edge and with internal denticles. The inner part of the peristome shows an appressed parietal callus continued into a foliated columellar callus, which has a raised edge overhanging the siphonal canal on large specimens, and bears indistinct ridges towards the edge. The colour pattern is very characteristic, with articulated spiral bands of light patches on the knobs and dark brown in the interspaces, alternating with medium brown uniform bands.
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Shark skin is almost entirely covered by small placoid scales. The scales are supported by spines, which feel rough when stroked in a backward direction, but when flattened by the forward movement of water, create tiny vortices that reduce hydrodynamic drag and reduce turbulence, making swimming both more efficient and quieter compared to that of bony fishes. It also serves a role in anti-fouling by exhibiting the lotus effect. All denticles are composed of an interior pulp cavity with a nervous and arterial supply rooted in the dermis to supply the denticle with mucus.
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Left to right: denticles of Paralogania (?), Shielia taiti, Lanarkia horrida The bony scales of thelodonts, the most abundant form of fossil fish, are well understood. The scales were formed and shed throughout the organisms' lifetimes, and quickly separated after their death. Bone, a tissue that is both resistant to mechanical damage and relatively prone to fossilization, often preserves internal detail, which allows the histology and growth of the scales to be studied in detail. The scales comprise a non-growing "crown" composed of dentine, with a sometimes-ornamented enameloid upper surface and an aspidine base.
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Alternatively, workers may be subterranean associates of attines and thus not accessible to standard collection techniques. The mandibular dentition of reina is highly distinctive and unlike any other Megalomyrmex species. In other species the dentition varies from a condition of few teeth that gradually decrease in size basally to one in which the two apical teeth are much larger than a series of diminished basal denticles. In contrast, M. reina has a single large apical tooth, which is long and sharp, followed by a relatively uniform series of smaller teeth.
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The palate (roof of the mouth) is similar to that of Chenoprosopus and other early temnospondyls. The bones of the palate are covered with small, dome-like structures known as denticles. The interpterygoid vacuities (holes between the pterygoid bones which were characteristic of temnospondyls) were relatively small and semicircular, located more than halfway towards the rear of the skull. Their small size and rearward location means that their outer edge was completely formed by the pterygoid bones, without any contribution from other palatal bones at the edge of the skull.
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This description is based on parthenogenetic female specimens. Its body possesses a well-expressed dorsal keel, and is relatively high and oval. Its posterodorsal angle is rounded, while the posterior margin can be moderately concave. The posteroventral angles are provided with 1–3 small denticles with broad bases, which carry small setules between them. It shows a row of approximately 100 short setules along the posterior margin of the inside of its carapace. Its ventral margin can be irregularly convex, with about 35–40 ventral setae, 8 of which are long.
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The tulip shell has a fusiform outline, with an overall smooth surface, and presents fine growth lines, and small denticles on the inner edge of its delicate outer lip. It is whitish to tan in color, with rows of darker brownish blotches of various sizes. Over the blotches are symmetrical rows of thin lines which spiral along the whorls of the shell, which are normally about 9 in number. The shell of an adult tulip snail can be from 2.5” to 9.5” inches (6.4 – 24.1 cm) in length.
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Murphydoris singaporensis Sigurdsson, 1991 is the type species of the monotypic genus Murphydoris. The generic name Murphydoris was created to honor the zoologist and ecologist D. H. Murphy, who is on the staff at the National University of Singapore. The characteristics of the genus Murphydoris is, that it lacks peri-anal ctenidia (comb-like respiratory gills); its rhinophores are non-lamellate and its radula formula is n x 1.1.0.1.1. The lateral teeth are unicuspid (= with a single tapering point) with 12 denticles and the marginal teeth are bicuspid.
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The tip of the distal end has a small cap of dermal bone with small pits and denticles for clinging on to the female. The proximal part of the clasper expands into a plate with four foramina, two larger above two smaller. It is thought that this anatomy corresponds to the core of an erectile element as in extant sharks. Female Incisoscutum specimens differ from these male claspers and instead fossils have been found with a broad based pelvic plate that articulates with a posteriorly directed basipterygium, similar to modern sharks.
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The third lateral has a quadrangular body, with a simple cusp. The fourth lateral is very large, its body irregular, its cusp long, serrated on both sides, but this is only visible on the upper side in its normal position. The uncini, the number of which I cannot ascertain, are long, slender, and apparently smooth, though in some of them, a few very small denticles are present, but they are only visible in an expanded position. The bodies of the median teeth are brown especially towards the centre.
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Mola alexandrini has a relatively small mouth and its teeth fused into a parrot-like beak. It can reach up to in length and 2,300 kg in mass, making it one of the two heaviest bony fish on Earth, only matched by its congener, the ocean sunfish. Their body is flat and round, with large fins that they swish back and forth to propel themselves with as they swim horizontally. Their skin has rough denticles, leathery texture, with brown and gray coloring with pale blotches until death when they turn white.
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Lasiognathus is a genus of deep-sea anglerfish in the family Thaumatichthyidae, with six species known from the Atlantic and Pacific Oceans. It has been called a "compleat angler", in that its lure apparatus appears to consist of a fishing rod (the projecting basal bone or pteropterygium), a fishing line (the illicium, a modified dorsal fin ray), bait (the bioluminescent esca), and hooks (large dermal denticles). It is also distinctive for an enormous upper jaw with premaxillaries that can be folded down to enclose the much shorter lower jaw.
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The armor was fused to its spine, and its limbs were situated in normal positions, unlike the turtle, where they are located inside the ribcage. The weak limbs of Henodus suggest it spent little, if any time on land. Henodus also had a single tooth on each side of its mouth, though the remaining teeth were replaced by a beak. In addition, it had baleen-like denticles along the jaws, which combined with a unique feature of the hyoid and musculature indicative of rapid jaw closing indicate a filter feeding lifestyle.
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It is an acaule plant, with an underground stem 30 cm long and 25 cm wide. Occasionally, a small portion of the stem may come out of the ground. The leaves, from eight to ten, are opaque and flat, 80–120 cm long and bluish or silvery green in color. The leaflets, 15–18 cm long, are arranged on the rachis in the opposite way at an angle of 150-180º and are covered with a thick, waxy layer which, when rubbed, releases a characteristic odor; the margins are whole and equipped with small denticles.
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The upper edges of the antennomeres have a point on the upper inner sides, giving the antennae a slightly serrate appearance. The mandibles have a distinct cup-like appearance, with the inner side of each cup towards the clypeal surface and a single tooth is present on the lower apex. The front of the inner margins on the mandibles each have a row of thick setae while rows of denticles run along the dorsoventral edge. The modified labrum has a rounded, tongue like look extending between the mandibles.
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The wings are shortened, the forewings being about and the hindwings . There are a total of fourteen hamuli on the hindwings, all but one located towards the wing tip, with the last just to the base side of the Rs vein. The forewings have a very large parallelogram shaped DC cell and a DC2 cell, which is not seen in wings of Sphecomyrma or Gerontoformica species. Unlike the described Camelomecia females, the male has only eleven antennae segments, and the clypeus lacks denticles, rather a brush of fine setae is present.
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The dermal denticles are widely spaced, highly variable in size, and have 1-3 ridges and cusps. This shark is a dark gray above, with faint blackish saddles mostly broken up into irregular blotches, and a smattering of lighter spots. There are also blackish bars below the eyes, over the gills and pelvic fins, and on the upper caudal fin lobe before the ventral notch. The underside is pale with many gray blotches, and black and white speckling on the snout; the demarcation between the dorsal and ventral coloration is irregular but abrupt.
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The marbled electric ray can be identified by its ornate color pattern and fringed spiracles. The body of the marbled electric ray is soft and flabby, and entirely lacks dermal denticles. The thick pectoral fin disc is nearly circular and comprises about 59–67% of the total length; the paired kidney- shaped electric organs are visible beneath the skin, outside of the small eyes. Immediately posterior to each eye is a large, oval spiracle, which bears 6–8 long, finger-like projections on the rim that almost meet at the center.
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The fish is carnivorous, with its prey consisting mainly of benthic invertebrates and fishes. Such food items include polychaetes, gastropods, bivalve mollusks, rock crabs, cancer crabs, spider crabs, lobsters, shrimps, squids, and fishes including spiny dogfish, alewife, Atlantic herring, menhaden, hakes, sculpins, cunner, tautog, sand lance, butterfish, and various flounders. Juveniles primarily subsist on benthic invertebrates such as polychaetes, copepods, amphipods, isopods, crangon shrimp, and euphausiids. Individuals have been found with the denticles on the snout worn smooth, indicating that the snout is used to dig in the mud or sand to obtain bivalve mollusks.
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One bone in particular, identified as a supraorbital, included a short spike which would have projected outwards over the eye. The leaf-shaped teeth are asymmetrical, with the majority of the denticles on the edge closest to the tip of the snout. These teeth are also proportionately large compared to those of other ankylosaurs, with the largest measuring 10 millimeters (0.4 in) across. This compares to the much larger North American Euoplocephalus, 6–7 m (20–23 ft) in body length, which had teeth averaging only 7.5 mm (0.3 in) across.
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At up to , by far the heaviest freshwater member of the family is the short-tailed river stingray, which among South American strict freshwater fish only is matched by the arapaima (Arapaima) and piraíba catfish (Brachyplatystoma filamentosum). In each species in the family Potamotrygonidae, females reach a larger size than the males. The upper surface is covered with denticles (sharp tooth-like scales). Most species are brownish or greyish and often have distinctive spotted or mottled patterns, but a few species are largely blackish with contrasting pale spots.
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The anterior margins and the trailing tips of the pectoral fins are both concave, and they are incised deeply near the tail. Visible thorns (denticles) are only found near the eyes and in a single row on the top of the tail. Like many other skates and rays, the eggs of the prickly brown ray have horn-like projections. Dipturus teevani can be distinguished from other rays in its genus by its long snout (22% of total length), which forms an acute angle with the pectoral fins (around 70°).
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Hypothetical restoration, based on related genera Fossil theropod teeth are typically identified according to features including size, proportion, curvature of the crown and the morphology and number of denticles (serrations). The holotype of D. bornholmensis is a tooth crown long, from front to back and wide at the base. The front part of the tooth was worn, indicating that it was shed when the animal was alive. It was further affected by taphonomic wear; the base of the tooth is irregular, so it may have been slightly longer in life.
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The birdbeak dogfish (Deania calcea) is a dogfish shark of the family Centrophoridae found in the Pacific Ocean around Honshū, Japan, southern Australia, New Zealand, and Chile, and in the Atlantic Ocean from Iceland south to the Cape of Good Hope. The birdbeak dogfish has a very long, narrow snout, no anal fin, two long and low dorsal fins with grooved spines, small rectangular pectoral fins, and pitchfork-like denticles. It lives at depths between 73 and 1,450 m. It is ovoviviparous with up to 12 pups per litter.
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Adult sunfish range from brown to silvery-grey or white, with a variety of region-specific mottled skin patterns. Coloration is often darker on the dorsal surface, fading to a lighter shade ventrally as a form of countershading camouflage. M. mola also exhibits the ability to vary skin coloration from light to dark, especially when under attack. The skin, which contains large amounts of reticulated collagen, can be up to thick on the ventral surface, and is covered by denticles and a layer of mucus instead of scales.
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1822 illustration of the first Ptychodus teeth. Due to a well global distribution the Ptychodus is well represented in the fossil history; many fossils have been uncovered such as isolated teeth, fragments of dentition, calcified vertebral centra, denticles, and associated fragments of calcified cartilage. The very first remains of Ptychodus were found in England in the early 19th century and was characterized as "palates of fish". The first discovery of Ptychodus teeth in Kansas came in 1868 when Leidy reported and described a damaged tooth near Fort Hays, Kansas.
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The caudal fin has a well-developed lower lobe and a notch near the tip of the upper lobe. The dermal denticles are oval with five horizontal ridges leading to marginal teeth. The most distinctive trait of this species is its coloration: the back and dorsal fins are gray to yellowish gray, and the cephalofoil margins, flanks, underside, pectoral fins, pelvic fins, and anal fin are bright yellow to orange with a metallic or iridescent sheen. Newborn sharks are gray above, darkening on the first dorsal fin and upper caudal fin lobe, and whitish below.
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Diagram comparing the holotype tooth (first from left) with other spinosaurid teeth from Asia Fossil theropod teeth are typically identified by attributes such as the proportions, size, and curvature of the crown, as well as the presence and/or shape of the denticles (serrations). The holotype of S. suteethorni (specimen DMR TF 2043a) is in total length, with the crown being long, and wide at its base. It is among the larger teeth discovered by Buffetaut and Ingavat. One much smaller specimen (DMR TF 2043b) measures in length.
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It has better preservation of small details than the former specimens, such as visible, though poorly defined serrations, with two to three denticles per mm (0.039 in). Like GMNH-PV-999, it has a granular texture and at least 12 flutes on its surface, not all of which stretch to the crown's full length. Out of the four teeth attributed to "S." fusuiensis, specimen IVPP V 4793 is the most intact, although still somewhat deformed. The crown, which is missing its tip, is long and wide at the base.
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Life restoration Most of the teeth found with the holotype specimen were not in articulation with the skull; a few remained in the upper jaw, and only small replacement teeth were still borne by the lower jaw. The teeth had the shape of recurved cones, where slightly flattened from sideways, and their curvature was almost uniform. The roots were very long, and tapered towards their extremity. The carinae (sharp front and back edges) of the teeth were finely serrated with denticles on the front and back, and extended all along the crown.
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The tubemouth whipray (Urogymnus lobistoma) is a little-known species of stingray in the family Dasyatidae, named for its distinctive, highly protrusible jaws. It is found in shallow, brackish water near mangrove forests and large river mouths along the coasts of southwestern Borneo and southern Sumatra. Measuring up to across, this species has a diamond-shaped pectoral fin disc with an elongated, pointed snout and broadly rounded outer corners. The upper surface of the disc is a plain grayish or brownish in color, and covered by small, flattened dermal denticles.
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The Mekong freshwater stingray, Hemitrygon laosensis, is a species of stingray in the family Dasyatidae, restricted to the Mekong and Chao Phraya Rivers in Laos and Thailand; the occurrence in Chao Phraya is considered an introduction. Measuring up to across, this ray has an oval pectoral fin disc, a tail with both upper and lower fin folds, and a midline row of spine-like dermal denticles. A characteristic feature of this species is its bright orange underside. The Mekong freshwater stingray preys on invertebrates and is aplacental viviparous.
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The anal fin is larger than the second dorsal fin and is rounded in juveniles, becoming more angular in adults. The large caudal fin has a distinct lower lobe and a deep ventral notch near the tip of the upper lobe. The skin is thick and made rough by widely spaced, arrowhead-shaped dermal denticles with three horizontal ridges. The dorsal coloration is brown to gray with 9-10 dark saddles closely alternating with lateral blotches, including a large round blotch encompassing the gill slits; the fins are dark above with variably pale margins.
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The anal fin is rounded and much larger and deeper than the second dorsal fin. The medium-sized caudal fin has a distinct lower lobe and a strong ventral notch near the tip of the upper lobe. The body is densely covered by fine, arrowhead-shaped dermal denticles bearing median and lateral ridges. The dorsal coloration is unique among swellsharks, consisting of 31-34 closely spaced, transverse dark brown bars on a creamy yellow background; on the snouth the bars are irregular, while towards the tail every other bar becomes faint.
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The many teeth of a sawfish's saw are not actually teeth at all, but rather special types of scales known a dermal denticles. These protruding weapons, combined with the animal's ability to strike from side to side with great force, provide it with a powerful and efficient defense mechanism. Although the saw is mainly used for feeding purposes, observations of sawfish in captivity show that they may also be used for self-defense. When sharks or other marine creatures threaten them, they retaliate with three swift blows to the instigator's dorsum.
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The pelvic fins are small and triangular. The tail is whip-like and extremely thin, measuring 3–3.5 times as long as the disc when intact, and lacks fin folds. Usually one serrated stinging spine is located on the upper surface on the tail, some distance from the base. Adult rays have a wide band of flattened, heart-shaped dermal denticles that extend from between the eyes to the tail spine, increasing in density with age, along with two large pearl thorns at the center of the back.
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There were at least five teeth in each premaxilla, and at least nineteen in the maxilla and sixteen in the dentary of the lower jaw. However, the number of maxillary and dentary teeth were established with the incomplete skull of one of the first specimens found; the actual numbers might have ranged up to about two dozen, perhaps twenty-six for the lower jaw. The premaxillary teeth were somewhat longer and recurved. To the rear, they gradually approach the form of the maxillary teeth, beginning to show denticles.
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The skin is covered by overlapping dermal denticles; the denticle crowns are narrow and placed on narrow stalks, with three teeth on their posterior margins. The coloration is distinctive, consisting of a dense variegated pattern of dark markings ranging from tiny to larger than the eye, on a brownish background. In particular, there are three spots above a fourth curved spot, forming a "clown face", beneath each dorsal fin. The spots extend onto the dorsal and anal fins, and the upper surfaces of the pectoral and pelvic fins.
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The blades of the cephalofoil are folded back along the body, and long external gill filaments protrude from the gill slits. At a length of , the placenta has formed; the first teeth, dermal denticles, and skin pigmentation appear on the embryo, and the external gills are much reduced in size. By the time the embryo is long, it resembles a miniature version of the adult. Birthing takes place in May and June off Mumbai and Parangipettai, in March and April in the Gulf of Mannar, and in February and March off northern Australia.
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The specific epithet falciformis is Latin for "sickle- shaped", which refers to the outline of the dorsal and pectoral fins. The silky shark's common name comes from the fine texture of its skin compared to other sharks, a product of its tiny, densely packed dermal denticles. It may also be referred to as blackspot shark (usually used for C. sealei), grey reef shark (usually used for C. amblyrhynchos), grey whaler shark, olive shark, reef shark, ridgeback shark, sickle shark, sickle silk shark, sickle-shaped shark, silk shark, and silky whaler.
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The daisy stingray, Dasyatis margarita, is a little-known species of stingray in the family Dasyatidae, found in shallow waters along the coast of West Africa. This species typically grows to across and has a rounded pectoral fin disc and (in adults) a wide band of dermal denticles over its back. It is characterized by a greatly enlarged, nacreous denticle in the middle of its back called a "pearl spine"; this feature is shared with the similar but much smaller pearl stingray (D. margaritella), which has often been confused with this species.
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The pearl stingray (Dasyatis margaritella) is a little-known species of stingray in the family Dasyatidae, found in shallow coastal waters from Mauritania to Angola. Growing to across, this species has a rounded pectoral fin disc with a pointed snout, and a wide band of dermal denticles over the back in adults. It closely resembles and is often confused for the much larger daisy stingray (D. margarita); both species are characterized by the presence of an enlarged, nacreous denticle in the middle of the back called a "pearl spine".
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The following maxilla bone had about 40 teeth, which were generally small except for a "canine" region of four or five larger teeth near the front part of the bone. All of the teeth were only preserved as broken stumps at best, so specific information about their shape is unobtainable. The front part of the palate (roof of the mouth) has large, elliptical choanae (internal nostrils) separated by narrow, toothless vomer bones. Most of the palate was formed by the plate-like pterygoid bones, which were covered with tiny denticles.
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The area between the antennae is raised and carinae run from just under the antennae to just below the front edges of the compound eyes. The antennae are formed of twelve segments totaling approximately . There is a row of setae running above the upper margin of the clypeus, a second row running along the middle of the clypeus and row of notably elongated setae running along the front edge. Though obscured partially in the described fossils, there are over twenty five denticles running the length of the clypeus front edge.
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G. rugosus holotype The single described worker of G. rugosus has distinct ridged texturing of the exoskeleton that runs along the mesosoma and metasoma. The rectangular head has raised cuticle between and behind the antennae, and extends down to the back margin of the clypeus. The compound eyes are smaller than seen in the other species, with an elongated outline, and placed closer to the articulation point with the body than to the clypeus. The lower edge of the clypeus has 32 denticles, and the front side edges obscure the mandible bases.
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There is a deep fin fold running beneath the tail from the level of the spine almost to the tip. The skin is mostly smooth, save for small dermal denticles found along the middle of the back from the spiracles to the tail spine, as well as three thorns on the "shoulders". The coloration is dark gray to brown to olive above, with various darker mottling, and off-white below. This species typically grows up to across and long, though it has been reported to a length of .
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The developing fetuses are initially nourished by a yolk sac, and later on exhibit oophagy, in which they consume infertile eggs produced by their mother (and possibly also uterine fluid). There is no evidence of sibling cannibalism as in the sand tiger shark (Carcharias taurus). Unborn embryos are similar in appearance to adults, with proportionally larger heads and eyes. They are covered with a thin layer of epithelium that prevents the uterine wall from being abraded by the embryo's sharp dermal denticles; this has not been observed in the young of other thresher sharks.
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They have no spinous dorsal fin, absent or reduced scales, sandpapery denticles on various areas of the body, and a reduced gill opening. Identification of species is determined in part through color, pattern, and the presence and number of spines and fleshy tabs, or lappets, on the skin (Robins & Ray 1986). The checkered puffer is pale tan to yellowish with a polygonal or square network of lines centered on a bulls-eye pattern on the midback in front of the dorsal fin. Lines are dark gray to olive, with small, dark brown spots on cheeks and lower sides.
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Several rows of denticles are also present along the palatine bones along the rim of the mouth, but apparently not the ectopterygoid bones immediately behind the palatines. The rear of the palate possesses a bone known as a parasphenoid, which has acquired an unusually complex dart-like shape. The pterygoids each have a thin rear branch that reaches as far back as the jaw joints, while further towards the front of the skull they converge together. Perhaps the most notable feature of the palate is the fact that the rear branches of the pterygoids are simple, with concave outer edges.
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Handfish grow up to long, and have skin covered with denticles (tooth-like scales), giving them the alternate name warty anglers. They are slow-moving fish that prefer to 'walk' rather than swim, using their modified pectoral fins to move about on the sea floor. These highly modified fins have the appearance of hands, hence their scientific name, from Latin bracchium meaning "arm" and Greek ichthys meaning "fish". Like other anglerfish, they possess an illicium, a modified dorsal fin ray above the mouth, but it is short and does not appear to be used as a fishing lure.
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The dwarf black stingray (Hemitrygon parvonigra) is a little-known species of stingray in the family Dasyatidae, found off northwestern Australia and perhaps throughout Southeast Asia at depths of . Growing to a width of , this species is characterized by an angular, diamond-shaped pectoral fin disc with a short row of spear-like thorns along the midline of the back and few dermal denticles elsewhere. Its tail bears a long fin fold along the bottom and a much shorter ridge along the top, both past the stinging spine. Plain brownish in color above, this ray can range from light to very dark.
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The leopard whipray (Himantura leoparda) is a little-known species of stingray in the family Dasyatidae, found in the Indian and Pacific Oceans from South Africa to Australia. It is found close to shore at depths shallower than , over soft substrates. Attaining a width of , this species has a diamond-shaped pectoral fin disc with a pointed snout and an extremely long, whip-like tail without fin folds. Adult rays have a leopard-like dorsal pattern of dark brown rings on a yellowish brown background, as well as a row of enlarged, heart- shaped dermal denticles along the midline of the disc.
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The tail is distinctive, being shorter than the disc and ending bluntly rather than tapering to a filament as in other Dasyatis species. However, Nishida and Nakaya (1990) consider that tail damage in stingrays is common and not always obvious. There are two stout, saw-toothed spines placed near the base of the tail, and behind them a ventral fin fold; different sources conflict on whether there is also a dorsal fin fold. The skin is largely smooth, except for numerous small dermal denticles over the posterior portion of the disc, the pelvic fins, and the base of the tail.
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The subequal jaws are anteriorly lined with rows of numerous close-set, depressible, and retrorse teeth; vomerine teeth are absent. Footballfish females differ from those of other ceratioid families by their shortened, blunt snout; along with the chin, it is covered in sensory papillae. Originating above or slightly in advance of the small eye is an illicium (the "fishing rod") and at its end a bioluminescent, bulbous esca (the "fishing lure", its light owing to symbiotic bacteria). Escal morphology varies between species, and it may or may not possess denticles or accessory appendages, the latter either branched or unbranched.
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The caudal fin is asymmetrical, with a strong lower lobe and a longer upper lobe with a ventral notch near the tip. The dermal denticles are overlapping and bear three horizontal ridges (five in larger individuals) leading to marginal teeth. This species is bronze to gray above and white below, with a white stripe on the flank. A thin black line runs along the leading margins of the dorsal fins, pectoral fins, and the upper caudal fin lobe, as well as the caudal fin trailing margin; the lower caudal fin lobe and sometimes the pectoral fins are also tipped in black.
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Golden eagle with a European hare Tyrannosaur tooth marks are the most commonly preserved feeding traces of carnivorous dinosaurs. It is usually not possible to identify tooth marks on bone made by small predatory dinosaurs due to similarities in the denticles on their teeth. However, there are exceptions, like an ornithomimid caudal vertebra that has tooth drag marks attributed to Saurornitholestes and a partial Troodon skeleton with preserved puncture marks. Small bones of small theropods that were preyed upon by larger ones may have been swallowed whole and digested frequently enough to affect their abundance in the fossil record.
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Early illustration of a Portuguese dogfish. The first scientific description of the Portuguese dogfish was published by Portuguese zoologists José Vicente Barbosa du Bocage and Félix António de Brito Capello, in an 1864 issue of Proceedings of the General Meetings for Scientific Business of the Zoological Society of London. They created the new genus Centroscymnus for this shark, and gave it the specific epithet coelolepis, derived from the Greek ' ("hollow") and lepis ("fish scale") and referring to the structure of the dermal denticles. The type specimen, caught off Portugal, has since been destroyed in a fire.
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The very large dermal denticles change in shape with age: in juveniles, they are widely spaced and heart-shaped with an incomplete midline ridge and three posterior points, while in adults they are overlapping, roughly circular, smooth, and flattened with a round central concavity, superficially resembling the scales of bony fishes. Young sharks are a uniform blue-black in color, while adults are brown-black; there are no prominent fin markings. In 1997, a partially albino individual, with a pale body but normal eyes, was caught in the northeastern Atlantic. This represented the first documented case of albinism in a deep-sea shark.
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Denticles contain riblet structures that protrude from the surface of the scale; under a microscope this riblet can look like a hook or ridges coming out of the scale. The overall shape of the protrusion from the denticle is dependent on the type of shark and can be generally described with two appearances. The first is a scale in which ridges are placed laterally down the shark and parallel with the flow of the water. The second form is a smooth scale with what looks like a hooked riblet curling out of the surface aiming towards the posterior side of the shark.
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The blurred lanternshark (Etmopterus bigelowi) is a little-known species of dogfish shark in the family Etmopteridae, found around the world in benthic and pelagic habitats from a depth of to over down. This shark forms the E. pusillus species group with the smooth lanternshark, which are distinguished from other members of its family by having irregularly arranged, flat-topped dermal denticles that give them a "smooth" appearance. Both species are slender-bodied with long heads, two dorsal fins bearing spines, no anal fins, and light-emitting photophores. The blurred lanternshark is larger, reaching or more in length.
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On the contrary, the latter has very symmetrical teeth with moderate denticles. The respective indistinct and specialized dentition of Erlikosaurus and Segnosaurus indicates that these two therizinosaurids were separated by niche differentiation in food acquisition, processing, or resources. This conclusion is strengthened by the large difference in estimated body masses, which is up to 500%. Life restoration of the larger and sympatric Segnosaurus In a 2017 study of niche partitioning in therizinosaurs through digital simulations, Lautenschlager found the straighter and more elongated dentaries of primitive therizinosaurs had the highest magnitudes of stress and strain during extrinsic feeding scenarios.
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The muscular, lobe-like pectoral fins of the taillight shark suggest they may be used for propulsion, in a manner more akin to that of chimaeras than other sharks or at least for hovering in the water column. Its strongly built jaws and teeth likely allow it to tackle relatively large prey. On the belly in front of the cloaca is a pouch-like groove devoid of denticles and lined with a luminescent tissue formed into numerous, tightly packed papillae (nipple-like structures). The entrance to the pouch is a slit lined with folds of skin.
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The diagnostic features of the genus Apateon are tabular horns separated from the skull table by a groove; tooth-bearing region of maxilla is broad and the dorsal osteoderms are smooth or with radiating striations. The diagnostic features of the Melanerpeton group are the palatine, the ectopterygoid and palatine ramus of pterygoid are extremely delicate, poorly ossified and have few or no denticles. The Melanerpeton genus has no autapomorphies and is paraphyletic with respect to the Leptorophus- Schoenfelderpeton group. The Leptorophus-Schoenfelderpeton group is characterized by a postorbital separated from supratemporal, a carotid foramina and grooves situated on sides of the cultriform process.
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The pelvic fins are about as large as the second dorsal fin, with rounded tips and nearly straight trailing margins. The caudal peduncle is short and leads to a broad caudal fin comprising less than a quarter of the total length; the upper lobe has a convex upper margin leading to a squared-off tip, while the lower lobe is indistinct. The skin is densely covered by tiny dermal denticles; each one is recurved and thorn-like, rising from an irregular star-shaped base. This species is a plain dark brown above, darkening to almost black below, with white dorsal fin spines.
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The tooth rows number 37 in the upper jaw and 40 in the lower jaw; the teeth of adult males are pointed, while those of juveniles and females are blunt. The whip- like tail measures not quite twice the length of the disc and bears both dorsal and ventral fin folds behind a stinging tail spine; the ventral fold measures less than half as long as the disc. Some individuals lack a tail spine. The dorsal surface is roughened by a band of small dermal denticles, extending from the snout to the base of the tail.
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The Langobardisaurus skull morphology reflects its unique pattern of dentition. The front part of the upper jaw is toothless, although some grooves on the premaxilla have been mistaken to be teeth in the past despite their lack of enamel.. Past this toothless region of the snout, there were larger tricuspid (three-pronged) cheek teeth on the maxilla and a large molariform tooth which is elongated in anteroposterior direction. This molariform tooth was flattened, with its occluding surface bent inwards and covered with tiny denticles. The lower jaw featured a similar molariform tooth which occluded with the aforementioned upper counterpart.
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The pelvic fins are triangular. The tail is moderately thick at the base and tapers evenly to the tip; it can measure three times as long as the disc or more, and bears one or two serrated stinging spines positioned about one body length past the base. Behind the sting, there is a slender ventral fin fold. The upper surface of the disc is densely covered by dermal denticles almost to the margins; a transverse row of 1-3 enlarged thorns, with the central one the largest and pearl-like, is present in the middle of the back.
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The pelvic fins are short and rounded. The whip-like tail is twice or more the length of the disc, and bears a serrated stinging spine on the upper surface near the tail base. A long, narrow fin fold occurs beneath the tail, which eventually becomes a keel that runs all the way to the tail tip. Larger rays have three large, elongated tubercles in the middle of the back; the tail is roughened by small dermal denticles, along with an irregular row of conical tubercles on each side and several large, flattened tubercles in front of the spine.
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The anal fin is much larger and deeper than the second dorsal fin. The caudal fin has a distinct lower lobe and a strong ventral notch near the tip of the upper lobe. The body is densely covered by small, overlapping dermal denticles with a median ridge and a single cusp, though a few may be three-cusped. Adult sharks are variegated brown above, with 9–10 dark saddles over the body and tail, a dark blotch atop each pectoral fin, and a distinctive "V"-shaped dark marking at the tip of the caudal fin upper lobe; the underside is plain whitish.
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This is a species belonging to the group of C. atropurpureus, C. bathyrhaphe, etc., including species in which the base of the columella is scarcely toothed, but passes into the basal margin in a regular curve, bearing several subequal denticles. The columella above is inserted upon the side of the umbilicus instead of in the center of the axis as in the typical Clanculus (Clanculopsis) Monterosato, 1880. From Clanculus atropurpureus, which seems to be its nearest ally, Clanculus microdon differs in the larger size, variegated coloration, and irregularity of the spiral ribs on the upper surface.
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The slender tail measures 92% as long as the disc and tapers evenly to a long, low leaf-shaped caudal fin; there are subtle skin folds running along either side, but no dorsal fin. Two serrated stinging spines are placed atop the tail, about halfway along its length. This species is the only member of its family with dermal denticles. There are four rows of small, sharp, well-spaced thorns running along the middle of the back on the aft portion of the disc, along with a single similar row along the midline of the tail base, before the stings.
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It is an arborescent plant, with a stem up to 2 m long and with a diameter of 40 cm, at the base of which often some shoots grow. The leaves, arranged like a crown at the apex of the stem, are 60–80 cm long and bluish in color and sometimes twisted on their own axis. The lanceolate leaflets, 12–17 cm long, are arranged on the rachis in the opposite way, at an angle of 45º; the margins are whole and the lower one can be equipped with small denticles. The petiole is straight and equipped with small spines.
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The dorsal and anal fins are placed posteriorly, and the base of the dorsal fin is longer than that of the anal fin. In place of a caudal fin, the dorsal and anal fins merge into a clavus, formed by 18-20 fin rays. The central rays in the clavus are supported by the last vertebra and form an elongated triangular lobe; some authors believe these rays to be remnants of the larval caudal fin, though this is disputed. Their skin is covered with small dermal denticles that are finer than those of the ocean sunfish.
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That Saurornithoides mongoliensis might be more derived, higher in the tree, than Sinornithoides and Sinusonasus, is indicated by the lack of a fenestra promaxillaris, a small opening at the front side of the snout, and the possession of large denticles on the rear tooth edges as well as the presence of the high number of six sacral vertebrae. That S. mongoliensis might be more basal, lower in the tree, than Zanabazar and Troodon, is shown by the presence of a recessus tympanicus dorsalis, the upper one of three small openings on the side of the braincase, in the inner ear region.
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Rauhut doubted this interpretation in 2011, stating that MB R 1084 has more similarities than differences with Ceratosaurus? stechowi teeth, like the rounded cross section, only marginal curvature of the crown, a more convex lingual than labial side, and similar size and shape of the denticles. Thus, according to his analysis, only the ridge count and distribution were left as unique to MB R 1084. Rauhut noted that though baryonychines also have ridges on either side of their teeth, they are usually most developed at the rear of the tooth, whereas MB R 1084 lacks ridges on that side.
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Restoration Atlasaurus differs from Brachiosaurus relative to the estimated length of the dorsal vertebral column (assuming 12 vertebrae, ), in having a proportionately larger skull, a shorter neck (with at least 13 cervical vertebrae, shorter and more uniform in length than Brachiosaurus), a longer tail and more elongated limbs (humerus to femur ratio: 0.99; ulna to tibia ratio: 1.15). The teeth are spoon-shaped and have denticles. The lower jaw of Atlasaurus is about long, the neck was about long, the humerus long, and the femur about long. It has been estimated at in length, and in weight.
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There were around six to eight denticles per mm (0.039 in), a much larger number than in large-bodied theropods like Torvosaurus and Tyrannosaurus. Some of the teeth were fluted, with six to eight ridges along the length of their inner sides and fine-grained (outermost layer of teeth), while others bore no flutes; their presence is probably related to position or ontogeny (development during growth). The inner side of each tooth row had a bony wall. The number of teeth was large compared to most other theropods, with six to seven teeth in each premaxilla and thirty-two in each dentary.
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The family Pterygotidae would be erected by Clarke & Ruedemann in 1912, and new subgenera were named for Pterygotus by Ruedemann in 1935. These subgenera included Pterygotus (Curviramus) and Pterygotus (Acutiramus) and were differentiated from other Pterygotus by the curvature of the denticles (teeth) of the chelicerae. The name "Acutiramus" derives from Latin acuto ("acute" or "sharp") and Latin ramus ("branch"), referring to the acute angle of the final tooth of the claws relative to the rest of the claw. The species originally included in the subgenus were P. (A.) bohemicus, P. (A.) buffaloensis and P. (A.) macrophthalmus.
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Most of the other hindmost tooth crowns are damaged so their complete features are unknown. The additional carina on tooth 23 appears to have been fully denticulated while the denticles were restricted to the basal side of the crown in tooth 22. Segnosaurus was unique among all known theropods in possessing triple carinae. The 14th alveolus on the right dentary of the holotype is walled over by seemingly pathological (due to injury or disease) bone growth but the teeth in that part of the dentary are damaged so it is not possible to determine how the teeth were affected by this.
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Apart from some particularly large dermal bones that form parts of the skull, these scales are lost in tetrapods, although many reptiles do have scales of a different kind, as do pangolins. Cartilaginous fish have numerous tooth-like denticles embedded in their skin in place of true scales. Sweat glands and sebaceous glands are both unique to mammals, but other types of skin glands are found in fish. Fish typically have numerous individual mucus-secreting skin cells that aid in insulation and protection, but may also have venom glands, photophores, or cells that produce a more watery serous fluid.
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The tail measures twice as long as the disc, and is broad and flattened at the base. On its upper surface is at least one, often two serrated stinging spines. Past the spines, the tail quickly tapers to become whip-like and bears a well- developed keel above and a long, low fin fold beneath. There are wide patches of small dermal denticles with flattened crowns between the eyes and over the middle of the back, along with a midline row of enlarged thorns that become progressively longer until they reach the base of the sting.
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The disc is mostly smooth, except for a row of 2-18 small, thorn-like dermal denticles along the dorsal midline in adults and a single thorn on each "shoulder" in males. The coloration of this species is distinctive: the back is golden brown with the disc and pelvic fins edged by a thin blue line and then a dark brown band. There are dark brown blotches around the eyes, between the spiracles, and in two pairs behind the spiracles and further back on the disc. Adult males have blue coloring on top and at the tip of the claspers.
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The white-edge freshwater whipray (Himantura signifer) is an extremely rare species of stingray in the family Dasyatidae, native to four river systems in Southeast Asia. Measuring up to across, this ray has an oval pectoral fin disc and a very long, whip-like tail without fin folds. It can be identified by the presence of a sharply delineated white band running around the margin of its otherwise brown disc, as well as by its white tail and a band of dermal denticles along the middle of its back. This species feeds on benthic invertebrates and is aplacental viviparous.
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Previously it was thought that the dentary of Andreolepis did not contain true teeth, but instead harbored denticles. The lack of teeth and the recognition of initial denticle organisation suggested a basal phylogenetic position within the osteichthyes. It was even argued that the presumed dentary fossil of A. hedei is uninformative of dental evolution, as the fossil did not represent dental development, but rather development of the dermal skeleton. This would mean the tooth-like structures of Andreolepis neither match with teeth of chondrichthyans nor with those of osteichthyans and are more similar to the development of structures in dermal scales.
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Although Head had specifically redefined the Hadrosauridae, based on shared characteristics, to include Protohadros, Horner and colleagues adapted a taxon-based definition that excluded Protohadros and thus Eolambia. They also identified additional characteristics differentiating Eolambia from hadrosaurids: there are coarse denticles on the teeth of the dentary, and the coronoid process is weakly expanded. Quadrate of Eolambia Variance in recovered phylogenetic positions for Eolambia persisted in following years. In the 2009 description of Levnesovia, Hans-Dieter Sues and Alexander Averianov found that Protohadros occupied an intermediate position relative to Altirhinus and Probactrosaurus, being the sister group of Fukuisaurus.
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The crowns of the maxillary and dentary teeth have denticles on their edges and a swollen basis The ascending branches of the paired premaxillae notched the combined nasal bones, whereas the opposite was usual in ornithischians. The frontal bones were covered by a halo of fine ridges; these indicate the presence of ceratinous plates, as with modern turtles. At the front of the braincase, paired hatchet-shaped ossified orbitosphenoids formed the floor of the olfactory lobes of the brain. The skull of the neotype was damaged by a paleoichthyologist resulting in the detachment of triangular plates from the palate.
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The length of the shell reaches a length of 10 mm. A shell with an minute, elegant fusiform shape, very distinct from its congeners through its sleek appearance produced by the rapidly growing in volume of its 6½ slightly convex whorls, for the subtle reticulation and the low elevation of the ribs which gives it a pearly appearance, and finally for the softness of the shell and its golden-yellow to horny color.. The suture is impressed. The aperture is subovate with a simple outer lip with inconspicuous denticles. The short siphonal canal is slightly inflected.
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In 1992 David Weishampel and Ronald Heinrich reviewed the systematics and phylogenetics of Hypsilophodontidae. Hypsilophodontidae was supported as a monophyletic clade that encompassed "thescelosaurids", Hypsilophodon and Yandusaurus. The family was diagnosed by the absence of ridges that end as denticles in teeth (reversed in Hypsilophodon); presence of a single central ridge on dentary teeth; ossified sternal plates on torso ribs; and a straight and unexpanded shape of the prepubis. Their resulting cladogram is reproduced below: The following cladogram of hypsilophodont relationships depicts the paraphyletic hypotheses; the "natural Hypsilophodontidae" hypothesis has been falling out of favor since the mid- late 1990s.
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The tail is broad and flattened at the base, becoming slender and whip-like past the spine with a low dorsal keel and a well-developed ventral fin fold. There is a massive, circular pearl spine at the center of the disc. Young rays are otherwise smooth-skinned, while older rays over across gain a wide band of small, flattened, circular dermal denticles covering the median third of the back from between the eyes to the base of the tail, as well as small prickles covering the tail behind the sting. This ray is a plain grayish brown above, and whitish below.
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The tail is broad and flattened at the base and becomes thin and whip-like past the (usually) single, slender stinging spine on the upper surface. Past the spine, there is a low dorsal keel and a well-developed ventral fin fold. There is a medium-sized oval pearl spine in the middle of the back; rays over across also gain a band of small, heart-shaped or flattened circular dermal denticles covering the median third of the disc, from between the eyes to the base of the tail. The tail is covered by small prickles behind the spine.
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The upper toothless border of the dentary and a significant portion of the articular border for the predentary are missing, but given that both of these borders have minor lengths—about less than the 25% of the length of the dental battery—they indicate that the toothless area between the tooth row and the predentary was rather reduced—another trait present in hadrosauroids but lost in hadrosaurids. The predentary is represented by a complete element of specimen AMNH FARB 6369, which has a U-shaped form. Numerous and pointed denticles are preserved on the dorsal surface of the predentary, giving a serrated texture.
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The tail is much longer than the body and ends in a large, crescent-shaped caudal fin; the lower caudal fin lobe is more than half the length of the upper. The entire dorsal surface has a grainy texture from a dense covering of tiny dermal denticles. A thick ridge is present along the midline of the back, which bears a band of sharp, robust thorns. There are also a pair of thorn-bearing ridges in front of the eyes, a second pair running from above the eyes to behind the spiracles, and a third pair on the "shoulders".
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G. maraudera holotype The single described worker of G. maraudera is , slightly larger than the workers of G. magnus. The mandibles are distinct from other species in that they are not able to fully close against the clypeus due to their length. The lower front margin of the clypeus has a pointed projection on each side, and is smaller than other species, having a reduced look to it and being slightly covered in places. As typical for the genus, there is a row of denticles along the clypeus edge, numbering around 15, unlike the over 25 seen in G. magnus.
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G. tendir holotype Due to darkening of the cuticle in the holotype fossil, finer details such as ocelli location and suture structuring were undetectable. The head has an elongated structure, being consistently taller than it is wide and the small compound eyes are placed near the midpoint between the clypeus and the rear edge. At the back edge of the head the cuticle is raised into two small points. In both the G. tendir workers the middle of the clypeus is developed with a frontal lobe, and about twenty denticles are present on the front edge.
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The anal fin is nearly as large as the first dorsal fin and placed slightly ahead of the second dorsal fin. The caudal fin is large and broad, with the upper lobe longer than the lower and bearing a prominent ventral notch near the tip. The skin is thick and sparsely covered by large, well-calcified dermal denticles; each denticle has a diamond-shaped crown with three horizontal ridges. This shark is cream- colored with dark brownish to grayish mottling on the back and sides, and seven dark brown dorsal "saddles" on the body and tail.
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Galeus is a genus of catshark, belonging to the family Scyliorhinidae, commonly known as sawtail catsharks in reference to a distinctive saw-toothed crest of enlarged dermal denticles, found along the upper edges of their caudal fins. They are found in the Atlantic, the western and central Pacific, and the Gulf of California, inhabiting deep waters at or close to the sea floor. Members of this genus are rather small, slim sharks with firm bodies and thick, rough skin. Their heads are usually fairly long and pointed, and have large mouths with well-developed furrows at the corners.
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The pectoral fins are large and broad, and the anal fin is larger than the second dorsal fin. The short and broad caudal fin has an indistinct lower lobe and a prominent ventral notch near the tip of the upper lobe. The skin is thick and covered by well-calcified, arrowhead-shaped dermal denticles, which are more sparse in young sharks. The back and sides are light gray to brown, with an irregular pattern of close-set darker saddles and blotches along with many dark (sometimes light) spots, and a dark stripe from under the eye to the pectoral fin origins.
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Size compared to a human The spine is superficially inserted in the skin, where it grows and moves from a deep position in the dermis where trabecular dentine forms, to a superficial location where centrifugally growing lamellar dentine forms. The number of denticles per annual cycle vary with growth rate, and are independent dermal elements formed by the dermal papilla and secondarily attached by dentine to the spine proper. The density of denticulation also varies with the growth rate of the occipital spine. The ratio of length of denticulated region to total length of the spine changes throughout ontogeny.
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The Beartooth Butte Formation in Wyoming, where J. howelli fossils have been discovered, has been interpreted as a quiet, shallow estuarine environment. The fossil sites yielding J. rhenaniae in the Rhineland have also been interpreted as having been part of a shallow aquatic environment with brackish to fresh water. The chelicerae of Jaekelopterus are enlarged, robust and have a curved free ramus and denticles of different lengths and sizes, all adaptations that correspond to strong puncturing and grasping abilities in extant scorpions and crustaceans. Some puncture wounds on fossils of the poraspid agnathan fish Lechriaspis patula from the Devonian of Utah were likely caused by Jaekelopterus howelli.
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The prickly shark (Echinorhinus cookei) is one of the two species of sharks in the family Echinorhinidae (the other one is the bramble shark), found in the Pacific Ocean over continental and insular shelves and slopes, and in submarine canyons. Bottom-dwelling in nature, it generally inhabits cool waters deep, but it also frequently enters shallower water in areas such as Monterey Bay off California. This stocky, dark-colored shark grows up to long, with two small dorsal fins positioned far back on its body and no anal fin. It is characterized by a dense covering of thorn-like dermal denticles, hence its common name.
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The exquisite preservation of the original Transvaal skeletons allowed for delicate parts of the skeleton to be preserved. Among these parts include approximately three rows of tiny bones (branchial ossicles) covered with thin tooth-like structures (branchial denticles). These structures appeared near the neck of one of the skeletons, and almost certainly attached to the branchial arches of gills while the animal was alive. Although such bones are rare among stereospondyls and unknown in any other rhinesuchids, this may simply be due to the fact that the bones of other genera were preserved in more rough-grained sediments where such delicate bones could be broken or difficult to find.
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The small, blocky dermal denticles are densely but irregularly arranged, each with a flat, truncate crown. The coloration is brown or gray above, with a pale spot over the pineal gland, and black below extending in faint markings over the sides of the head, under the pectoral fins, over the pelvic fins, and below the caudal peduncle. Like other lanternsharks, the blurred lanternshark possesses a species- specific light-emitting photophores, which are not placed in prominent bands. The blurred lanternshark is very similar to the smooth lanternshark, but is larger and can be reliably differentiated by the number of turns in the spiral valve intestine (16-19 versus 10-13).
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The larval somatic features including ossified branchial denticles and larval-type sculpturing of the skull roof are lost. Postcranial features of transformed A. gracilis indicate that it was terrestrial and biting force had become a more important factor than suction. Despite this instance of metamorphosis, neoteny is nearly ubiquitous throughout branchiosaurids and most species remained in an aquatic environment throughout their life (however we should not rule out the possibility that this is a relic of terrestrial metamorphosed specimens not being well preserved). Neoteny is one of the major modes of heterochrony in which there is a modification in the timing or rate of development of certain features that is inherited.
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A stinging spine with strong serrations, measuring up to long and equipped with a venom gland at its base, is positioned about a third of the distance along the tail. A second or even third spine may also be present, as the spines are regularly replaced and new spines grow in before existing ones have been shed. The tail behind the spine bears a low cutaneous fold on top and a short, deep fold underneath. The body and tail are smooth, save for a few dermal denticles on the leading edge of the disk; older individuals may also develop a row of bony knobs along the midline of the back.
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The mouth is narrow, with 20 rows of distinctive hexagonal, high-crowned teeth in each jaw and five papillae on the mouth floor. The tail is broad-based, with a filamentous tip and a single venomous spine located well backwards of the pelvic fins. There is no upper tail fold; the high ventral tail fold measures 2-3 times the height of the tail but does not reach the tip. The disk surface is covered by a broad band of fine dermal denticles extending from near the tip of the snout to the upper surface of the tail, excluding the extreme margins of the disk.
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Left to right: denticles of Paralogania (?), Shielia taiti, Lanarkia horrida The bony scales of the thelodont group, as the most abundant form of fossil, are also the best understood – and thus most useful. The scales were formed and shed throughout the organisms' lifetimes, and quickly separated after their death. Bone – being one of the most resistant materials to the process of fossilisation – often preserves internal detail, which allows the histology and growth of the scales to be studied in detail. The scales consist of a non-growing "crown" composed of dentine, with a sometimes-ornamented enameloid upper surface and an aspidine (acellular bony tissue) base.
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The upper caudal fin lobe is enormously elongated as is characteristic of threshers, measuring about as long as the rest of the shark; the thin, gently curving lobe is held at a steep upward angle and has a notch in the trailing margin near the tip. The skin is covered by small, overlapping dermal denticles, each with three horizontal ridges and three to five marginal teeth. This species is metallic purplish brown to gray above, becoming more bluish on the flanks. The underside is white, which extends over the pectoral and pelvic fin bases; this pattern is in contrast to the pelagic thresher, which is solidly colored over these fins.
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Three rows of tiny bones (branchial ossicles) covered with thin tooth-like structures (branchial denticles) have been preserved near the neck of one specimen of Uranocentrodon. These bones almost certainly attached to the branchial arches of gills while the animal was alive. Although such bones are rare among stereospondyls and unknown in any other rhinesuchids, this may simply be due to the fact that the bones of other genera were preserved in more rough- grained sediments where such delicate bones could be broken or difficult to find. Although evidently Uranocentrodon had gills of some kind, it is difficult to determine what kind of gills they were.
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However, it is uncertain whether they intended to resurrect Figaro or were simply unaware of its synonymy with Galeus, and their use of the ventral denticle crest to define the genus posed taxonomic problems. In 2008, Commonwealth Scientific and Industrial Research Organisation (CSIRO) researchers Daniel Gledhill, Peter Last, and William White resurrected Figaro with additional defining characters, to contain F. boardmani and the new species F. striatus. The genus has since been generally accepted as distinct. One of the key characteristics of Figaro, the ventral crest of denticles on the caudal fin, is also present in several species of the genus Parmaturus, as well as the Springer's sawtail catshark (G.
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The rounded to angular anal fin is substantially larger than, and placed slightly behind, the second dorsal fin. The caudal fin is moderately large, with a distinct lower lobe and a strong ventral notch near the tip of the upper lobe. The dermal denticles are tiny and arrowhead-shaped, with a median ridge in males and both median and lateral ridges in females. This shark is light grayish to brownish above, with narrow dark lines that form a series of open-centered saddles and narrow rings from the head to the tail; some individuals have small, scattered yellow spots or a dark ring or spot atop each pectoral fin.
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The tail is flattened at the base and measures 75-91% as long as the disc; a prominent skin fold runs along each side, and a deep, lance-shaped caudal fin is found at the end. The upper surface of the tail bears a serrated stinging spine about halfway along its length; there is no dorsal fin. The skin entirely lacks dermal denticles. This species is a plain light green above, becoming lighter towards the edge of the disc, and off-white below, becoming purplish or pinkish towards the lateral margins of the disc; the ventral, lateral disc margins may also have a dark brown edge or blotches.
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The pincushion ray or thorny freshwater stingray (Dasyatis ukpam) is a little- known species of stingray in the family Dasyatidae, found in the rivers and lakes of West and Middle Africa. A heavy-bodied ray measuring up to across, this species can be distinguished by its rounded pectoral fin disk, reduced or absent stinging tail spine, and—in adults—numerous stout thorns covering its back and tail. In lieu of a long tail spine as in other stingrays, the pincushion ray employs these thorny denticles in defense. Seldom encountered since it was originally described, this species has been assessed as Endangered by the International Union for Conservation of Nature (IUCN).
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Unlike in most theropods, the carinae (cutting edges) of Siamosaurus teeth lack well-defined serrations, though unworn teeth do exhibit very fine denticles. Some teeth (including the holotype) have a wave-like double recurvature when viewed from the front or back, which Buffetaut and Ingavat compared to that seen in carnosaur teeth from the same formation and one Deinonychus tooth described by John Ostrom in 1969. The S. suteethorni holotype is symmetrically concave front to back, and bears 15 flutes (lengthwise grooves) on its lingual (inward facing) and labial (outward facing) surfaces. These flutes run from the base of the crown before stopping from the rounded tooth tip.
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The northern sawtail catshark (Figaro striatus) is a little-known species of catshark, and part of the family Scyliorhinidae, endemic to northeastern Australia. It is demersal in nature and inhabits the upper continental slope at a depth of . A small, slender species growing no longer than , the northern sawtail catshark is characterized by a series of dark, narrow saddles along its back and tail, and rows of prominently enlarged dermal denticles along the upper edge of its caudal fin and the underside of its caudal peduncle. The International Union for Conservation of Nature (IUCN) does not yet have enough information to assess its conservation status.
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The evolution of major temnospondyl clades: an inclusive phylogenetic analysis, Journal of Systematic Palaeontology, 11:6, 673-705, DOI: 10.1080/14772019.2012.699006 Rhineceps fossils are differentiated from other rhinesuchids by the following traits “presence of a vomerine depression immediately anterior to cultriform process of the parasphenoid; ectopterygoids with enlarged tusks at their anterior end; transverse vomerine tooth row anteriorly convex; quadrate condyles projected behind the tip of the tabular horns; vomers with a continuous raised field of denticles; parasphenoid plate wider than long; well-developed transversely wide ‘pockets’; internarial vacuity between nasals and premaxillae; mandible with two anterior meckelian foraminae; chordatympanic foramen located on the suture between the articular and the prearticular.”.
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The pre-antorbital fenestra, a small opening in front of or beneath the antorbital opening, is well developed in taxa like Diplodocus and Tapuiasaurus, is nearly absent, like in Camarasaurus and Euhelopus. There were about 12-13 total teeth in the maxilla of Europasaurus, fewer than in more basal taxa (16 teeth in Jobaria and 14-25 in Atlasaurus), but falling within the range of variation in Brachiosauridae (15 in Brachiosaurus to 10 in Abydosaurus). All of the unworn teeth preserved display up to four small denticles on their mesial edges. A small amount of the posterior tooth crowns are slightly twisted (~15º), but much less than in brachiosaurids (30-45º).
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The second dorsal fin measures about 67-77% as tall as the first and is similar in shape; there is no midline ridge between the dorsal fins. The anal fin is almost as large as the second dorsal fin and lies slightly behind; it has a deep notch in the posterior margin. The caudal fin is asymmetrical; the lower lobe is narrow and well-developed, while the upper lobe has a gently convex upper margin and a prominent notch in the ventral margin near the tip. The body is covered by small, overlapping oval-shaped dermal denticles bearing three or five horizontal ridges leading to marginal teeth.
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Other features include large ocelli, short scapes, 12 antennomeres, small eyes, and a clypeal margin that has a row of peg-like denticles. The genus Zigrasimecia was originally incertae sedis (uncertain placement) within Formicidae until a second species, Zigrasimecia ferox, was described in 2014, confirming its placement in the subfamily Sphecomyrminae. Due to the highly specialized mandibles, scientists believe that the ants exhibited habits no longer seen in extant ants. The highly movable head suggests that mobility was an important factor for them (probably for feeding behavior), and the rugose projections may have played a major role in nest excavation because the mandibles would have prevented such activity.
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Inticetus is distinguished from other archaic heterodont odontocetes by the following features: long and robust rostrum bearing at least 18 teeth per quadrant; the absence of procumbent anterior teeth; many large, broad-based accessory denticles in double-rooted posterior cheek teeth; a reduced ornament of dental crowns; the styliform process of the jugal being markedly robust; a large fovea epitubaria on the periotic, with a correspondingly voluminous accessory ossicle of the tympanic bulla; and a shortened tuberculum of the malleus.Olivier Lambert, Christian de Muizon, Elisa Malinverno, Claudio Di Celma, Mario Urbina and Giovanni Bianucci. 2017. A New Odontocete (Toothed Cetacean) from the Early Miocene of Peru Expands the Morphological Disparity of Extinct Heterodont Dolphins. Journal of Systematic Palaeontology.
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The phylogenetic hypothesis suggests an alternative evolutionary process based on a functional analysis of increasing numbers of teeth. A high number of teeth with enough interdental space and properly placed denticles (as in troodontids) would be an adaptation for cutting and ripping. On the other hand, an excessive number of teeth with no interdental space (as in Pelecanimimus) would be a functional counterpart of the cutting edge of a beak. Thus, increasing the number of teeth would be an adaptation for cutting and ripping, as long as the space between adjacent teeth was preserved...while it would have the effect of working as a beak if spaces were filled with more teeth.
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Barnacle growth on boat hull In the marine industry, there is an extremely large market and need for anti-fouling surfaces. In laymen's terms, fouling is known as the process by which something becomes encrusted with material from the surrounding environment such as barnacles, algae, and green sludge. Dermal denticles are an extremely promising area of research for this type of application due to the fact that sharks are among the only fish without build up or growth on their scales. Studies by the U.S. Navy have shown that if a biomimetic material can be engineered, it could potentially cause an increase of fuel savings in military vessels of up to 45%.
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Japanese ichthyologists Shigeru Shirai and Hiroyuki Tachikawa described the blurred lanternshark in a 1993 article in the scientific journal Copeia, as part of a taxonomic revision of the Etmopterus pusillus species group. Shirai and Tachikawa found that the species group comprises the smooth lanternshark (E. pusillus) and a hitherto unrecognized second species, which they named E. bigelowi in honor of Henry B. Bigelow (who, along with William C. Schroeder and Stewart Springer, first described the blurred lanternshark in 1955, but did not see it as being separate from E. pusillus). The E. pusillus species group is distinguished from other lanternsharks in having truncate (ending in a flat crown as though the tip were cut off), irregularly arranged dermal denticles.
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Restoration of S. productus with prey It is certain that Stethacanthus was a carnivore, and considering its small size probably fed on small fish, brachiopods, and crinoid ossicles like other sharks of its time. Additionally, as the spine- brush complex is rather a large structure, it seems likely that, in combination with the forward-facing denticles on the structure, it would have produced a drag force during fast locomotion. Therefore, Stethacanthus was probably a slow-moving shark. The fins of Stethacanthus were also smaller than in of the same size, and their teeth were also on the small side relative to other small Paleozoic sharks, suggesting that Stethacanthus may have been a bottom-dweller.
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Onchopristis numidus tooth, displaying the same enamel ribbing found in Atlanticopristis Sawfish evolved long snouts armed with rows of teeth on both sides, although these spines do not represent true teeth, but highly modified fish scales, or dermal denticles. This adaptation could be related to their feeding habits, such as sifting through sand/mud to search for food or to slash at prey. Like extant sawsharks, these spines were attached to the rostrum of sclerorhynchids like Atlanticopristis using ligaments, compared to modern sawfish which have their teeth attached via alveoli (tooth sockets). The longitudinal ribbing, or ridges, of enameloid that can be seen on sclerorhynchid teeth would have aided in the attachment of these ligaments.
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The genus was described from three partial specimens currently residing in the collections of the University of Michigan Museum of Paleontology in Ann Arbor, Michigan, USA. Specimen number 22206 U.M. is a complete and well preserved skull with some denticles, pectoral girdle and pectoral fins. The second and third specimens were found in a block of matrix from the same location as 2226 U.M.. Specimen 22207 U.M. is a portion of the caudal region of a paddlefish, while 22208 U.M. is a partial shoulder with associated pectoral fin. While the specimens were found close to each other, it is impossible to determine if they represent a single individual, and as such were described as three separate fish specimens.
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The dark collar of the cookiecutter shark is believed to act as a lure. The intrinsic green luminescence of the cookiecutter shark is the strongest known of any shark, and has been reported to persist for three hours after it has been taken out of water. The ventrally positioned photophores serve to disrupt its silhouette from below by matching the downwelling light, a strategy known as counter-illumination, that is common among bioluminescent organisms of the mesopelagic zone. The individual photophores are set around the denticles and are small enough that they cannot be discerned by the naked eye, suggesting they have evolved to fool animals with high visual acuity and/or at close distances.
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The illicium is also long, with a terminal esca and 2-3 bony hook-shaped denticles mounted on an appendage at the tip. The escal bulb is equipped with a flap of skin that allows adjustment of the emitted light. The sphenotic spines (above the eyes) are well-developed, as are the two articular spines (at the rear end of the lower jaw). The operculum is divided into two parts, with the dorsal part split into two (rarely three) branches. The pectoral fin lobe is small, short, and broad; the fin rays number 5 in the dorsal fin, 5 in the anal fin, 14–20 in the pectoral fins, and 9 in the caudal fin.
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One to three serrated, stinging spines are located atop the tail, approximately one-quarter of the total tail length back from the base. The upper surface of the disc has a granular texture and bears a broad central band of closely spaced, flattened heart-shaped dermal denticles, beginning between the eyes, becoming widest at the "shoulders", and extending to entirely cover the tail. One or more rows of large, spear-like thorns also run along the dorsal midline from the center of the disc to the base of the sting. Barring the possible spotted variant, this species is a uniform yellowish brown above, with the disc margin and underside white, and the tail gray past the sting.
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Other morphological characteristics of the teeth, such as the detailed form of the denticles and the presence of blood grooves, also seem to indicate carnivory. Though little is known directly about the predatory behavior of troodontids, Fowler and colleagues theorize that the longer legs and smaller sickle claws (as compared to dromaeosaurids) indicate a more cursorial lifestyle, though the study indicates that troodontids were still likely to have used the unguals for prey manipulation. The proportions of the metatarsals, tarsals and unguals of troodontids appear indicative of their having nimbler, but weaker feet, perhaps better adapted for capturing and subduing smaller prey. This suggests an ecological separation from the slower but more powerful Dromaeosauridae.
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The Izak catshark or simply Izak (Holohalaelurus regani) is a species of catshark, belonging to the family Scyliorhinidae, common off the coasts of South Africa and southern Namibia. It typically inhabits the outer continental shelf at depths of , with the males found deeper than the females and juveniles. The Izak catshark has a short, wide, flattened head and a robust body tapering to a long, slender tail. It can be identified by its ornate color pattern of dark brown spots (in juveniles) or reticulations and blotches (in adults) on a light yellowish background, as well as by the enlarged dermal denticles over its pectoral fins and along its dorsal midline from the snout to the second dorsal fin.
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Finally, its quadrate distal articular surface is not separated into two condyles by a sulcus, and has only a very shallow depression at the centre. Like other geosaurins, P. manselii have large robust teeth, with moderate to strong mediolateral compression. Other notable characters of P. manselii are the presence of a separation between premaxilla and nasal approximately subequal to the midline length of the premaxilla, carinae formed by a keel and true microscopic denticles, and a long mandibular symphysis to which 9 out of 13 dentary teeth are adjacent. In dorsal view, the lateral margins of the prefrontals have an inflexion point directed posteriorly at an angle of approximately 70 degrees from the anteroposterior axis of the skull.
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The chelicerae themselves were large, but with differentiated denticles out of which one was serrated, long and strongly inclined. The differences from other pterygotids on the basis of visual acuity and the morphology of the claws indicates that Acutiramus occupied an ecological role distinct from other members of the group and was a significantly less active predator. The weaker visual system and shearing claws of Acutiramus suggest that it might have been an ambush predator, or possible a scavenger, that fed on soft-bodied animals, feeding during the night or in otherwise low-light conditions. In Bohemia, pterygotid eurypterids occur in strata that were once marine environments, associated with common and diverse marine fossils.
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The tail is short, barely exceeding the length of the disc when intact, and has a broad and flattened base leading to usually two stinging spines. After the stings, the tail becomes slender and bears a long ventral fin fold and a much shorter, lower dorsal fin fold. Most of the body lacks dermal denticles; a midline row of 4–13 small, closely spaced thorns is present behind the spiracles, and another row of 0–4 thorns before the stings. The dorsal coloration is grayish green, becoming pinkish towards the disc margins; there is a dark mask-like shape around the eyes and a pair of small dark blotches behind the spiracles.
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Several characteristics unique to Limnarchia were identified when the clade was named in 2000. Most of these characteristics, called synapomorphies, relate to the shapes of bones on the underside and back of the skull. Limnarchian synapomorphies include the presence of a row of teeth stemming from the ectopterygoid bone on the palate, the maxilla bone touching the vomer near the edge of the palate (these bones are separated by an opening in euskelian skulls), and the lack of bony projections called denticles on the vomer. Other characteristic features of limnarchians include the extension of the lower jaw behind the jaw joint, and a small hole called the paraquadrate foramen at the back of the skull.
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The whitish underside of a largetooth sawfish showing its nostrils (near the base of the saw), mouth, and two rows of gill slits (at the base of either pectoral fin) largetooth (top), green (middle) and narrow sawfish (bottom). Notice especially the structure of the saw, tail and pectoral fins, and the position of the first dorsal fin compared to the pelvic fins Sawfish have a strong shark-like body, a flat underside and a flat head. Pristis sawfish have a rough sandpaper-like skin texture because of the covering of dermal denticles, but in Anoxypristis the skin is largely smooth. The mouth and nostrils are placed on the underside of the head.
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Tecovasaurus (te-KOH-va-SAWR-us) is an extinct Late Triassic amniote genus of unknown affinities, known only from teeth. It was initially described as a basal ornithischian dinosaur, subsequently reclassified as a member of the clade Archosauriformes of uncertain phylogenetic placement (Irmis et al. (2007), and later, taking into account the similarity of its teeth to the teeth of traversodontid cynodonts such as Dadadon (shared presence of teeth with sub-triangular crowns, enlarged denticles, and thecodont tooth implantation), as an amniote of uncertain affinities (Kammerer et al., 2012; though "based on dissimilarities in gross morphology and geographic separation" the authors considered it more likely that the taxon is indeed an archosauriform rather than a traversodontid).
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The esca is simple in black seadevils (with either a conical terminus or anterior and posterior ridges in some species), and both it and the illicium are free of denticles. The bioluminescence is produced by symbiotic bacteria; these bacteria are thought to enter the esca via an external duct (in at least two species, the esca is not luminous until this duct develops, suggesting the bacteria originate from the surrounding seawater). The bacteria, belonging to the family Vibrionaceae, are apparently different in each anglerfish species; the bacteria have yet to be cultured in vitro. The eyes of black seadevils are small; the pupil is larger than the lens, leaving an aphakic space.
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This estimate exceeds the maximum body size of all other known giant arthropods by almost half a metre even if the extended chelicerae are not included. Jaekelopterus is similar to other pterygotid eurypterids in its overall morphology, distinguished by its triangular telson (the hindmost segment of its body) and inclined principal denticles on its cheliceral rami (the moving part of the claws). The pterygotids, a group of highly derived ("advanced") eurypterids, differ from other groups in several features, especially in the chelicerae and the telson. The chelicerae of the Pterygotidae are enlarged and robust, clearly adapted for active prey capture, with chelae (pincers) more similar to the claws of some modern crustaceans, with well-developed teeth on the claws, relative to the chelicerae of other eurypterid groups.
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The pterygiophore of the illicium does not protrude from the snout, and there is no hyoid barbel. At maturity, the streamlined males have an enlarged posterior nostril (with 10 – 17 lamellae); slightly ovoid eye with an enlarged pupil creating a narrow anterior aphakic space; no ilicium or esca; and the head and body is covered in dermal spinules, those along the snout midline being enlarged. The jaw lacks teeth, whereas those of the denticular bone have fused into a larger mass; the upper denticular bone possesses 10 – 17 hooked denticles. In both sexes, the fins are spineless: the single dorsal fin with 5 – 6 soft rays, the pectoral fins with 14 – 18, the anal fin with four, and the caudal fin with 19.
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Size of S. productus Stethacanthus was about long, and in many respects, had a shark-like appearance. However, it is best known for its unusually shaped dorsal fin, which resembled an anvil or ironing board. Small spikes (enlarged versions of the dermal denticles commonly covering shark skin) covered this crest, and the ratfish's head as well. The crest may have played a role in mating rituals, aided in clamping to the belly of larger marine animals, or been used to frighten potential predators.Elasmo-research Like other members of Stethacanthidae, Stethacanthus had unique pelvic girdles, single-crowned and non-growing scales, a pectoral fin composed of metapterygium with an accompanying ‘whip’ attached and a distinctive first dorsal fin and spine, termed the spine-brush complex.
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Both mola species have no caudal bones, ribs, and pelvic fins and have fused vertebrae, leaving only their median fins to propel themselves. It can be recognized from the Mola mola by their lesser number of ossicles and lacking the vertical band of denticles at its base. Bump head sunfish, dwarfs diver The fish of the family Molidae are characterized by their compressed shape, fused teeth, absence of spines in dorsal and anal fins, and a short caudal fin (Yasemi and Narari Bejgan, 2013) and can grow to great sizes. M. alexandrini was found to be synonymous with M. ramsayi in July 2017 and can be distinguished by their unique characteristics of head bump, a chin bump, rectangular body scales, and rounded clavus.
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The short and broad caudal fin has an indistinct lower lobe and a ventral notch near the tip of the upper lobe. The skin is very thick and bears well-calcified dermal denticles; each denticle has an arrowhead-shaped crown with three posterior points, mounted on a short stalk. The dorsal coloration is distinctive, consisting of 5-7 thick, parallel, dark stripes running from the snout to the caudal peduncle on a variably grayish or brownish background; the stripes become broken near the tail and the belly. In some sharks, the main stripe on either side may fork behind the eye, the stripes may be split in two by lighter central lines, or one or more large dark spots may be present.
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As fractions of seconds can determine whether or not a swimmer wins, Fairhurst and her team focused on finding the right material and design for the new Speedo suit. Their goal was to find a material that reduces skin friction in water, and Fairhurst found hydrodynamic animals particularly interesting. In the end, her team zeroed in on sharks as they saw the little ridges in their skin as being able to reduce the friction that swimmers would face. After this research, Fairhurst and her team would display their research to Speedo, and Speedo would go on to build a suit with material that mimiced the surface of shark skin and with denticles that patterned the same ridges within a shark’s skin.
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There is band of heart-shaped tubercles on the upper surface of the disc extending from before the eyes to the base of the sting; there is also a midline row of four to six enlarged tubercles at the center of the disc. The remainder of the disc upper surface is covered by tiny granular denticles, and the tail is covered with sharp prickles past the sting. This species is plain grayish brown above, often with a yellowish or pinkish tint towards the fin margins; in life the skin is coated with a layer of dark brown mucus. The underside is white with broad dark bands, edged with small spots, on the trailing margins of the pectoral and pelvic fins.
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Tooth of the related genus Spinosaurus, Museo di Storia Naturale A. Stoppani, Lombardy Fowler in 2007 put forward the possibility of spinosaurids having evolved from ceratosaurian ancestors, given that baryonychine teeth have ridges on their crowns reminiscent to those seen on the premaxillary and dentary teeth of Ceratosaurus. In 2008, Buffetaut rejected this proposal, citing that the D-shaped cross section of said Ceratosaurus teeth is not present in those of baryonychines. The main difference between MB R 1084 and all other known spinosaurid teeth, as Buffetaut noted, was in the large size of the denticles borne by the carinae. This led him to hypothesize in 2008 that spinosaurid dental evolution was largely characterized by the shrinking and eventual loss of serrations.
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Hindmost dentary teeth showing the third cutting edge (lc), unique to Segnosaurus among theropods Zanno and colleagues stated in 2016 that therizinosaurs were generally accepted to fall within the spectrum of omnivory and herbivory, with a trend towards intensified herbivory. While various anatomical features have been used to support this idea, tooth morphology had been considered relatively simplistic and with few unique specializations compared to other herbivorous dinosaurs. The few modifications include the increased symmetry in the teeth of Erlikosaurus and the enlargement of denticles in Segnosaurus. Zanno and collegaues identified novel, complex features in the dentary teeth of Segnosaurus, including the presence of additional carinae and folded carinae with denticulated front edges, which indicate Segnosaurus had a higher degree of oral food processing than other therizinosaurs.
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The plates comprising the carapace and plastron were already in the modern form, although there were additional plates along the margins of the shell that would have served to protect the legs. Also unlike any modern species of turtle, its long tail had spikes and terminated in a club, its head could not be retracted under the shell and its neck may have been protected by small spines. While it had no teeth in its jaws, it did have small denticles on the palate. The beak like structure suggests that the Triassic stem-turtles evolved from carnivorous stem-turtles to herbivorous as the loss of teeth and gain of the beak would benefit the crushing of plants in these stem-turtles.
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A partial Ventastega cheekplate consisting of the jugal, and parts of the lacrimal, quadratojugal, squamosal, and preopercular is convex in the vertical plane, indicating that Ventastega's skull was low in height. The preopercular in this specimen and several other partial skull fragments is a primitive tetrapod character, otherwise seen only in Ichthyostega, Acanthostega, and Crassigyrinus. The cephalic lateral lines in Ventastega have an intermediate morphology with the lines only being partially enclosed, between the primitive state of full enclosure of the lines in fish and Ichthyostega, and the fully open lines seen in Temnospondyls and other derived tetrapods. The ventral surface of the Ventastega pterygoid is covered is covered in denticles, a feature shared by all early tetrapods except Ichthyostega.
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Shell up to 12.0mm in length, ovate and soild, some specimens broader than others, teleconch of only 3-3 ½ convex whorls, protoconch of 1 ½ embryonic whorls, partly macroscopically axially striate; shell smooth except for very fine axial growth lines and a heavy, flattish spiral cord at base of body whorl. Aperture moderately narrow, outerlip thickened but not strongly variced, interior with 4-5 denticles decreasing in size anteriorly. Columella concave and with a moderately broad and thick callus, a strong fold at the anterior end and occasionally with another weak plication; siphonal notch deep and broad, parietal denticle swollen, anal canal distinct. Color fawn to brown, last whorl decorated with a moderately broad, interrupted brown subsutural band and a broad dark brown band on the posterior half.
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Distinguishing features of Liaoningotitan include a ventral margin of the maxilla that is convex, an upper tooth row that is short and anteriorly positioned; an anterior extension of the jugal that nearly reaches the level of the anterior margin of the antorbital fenestra; a basally constricted quadrate wing of the pterygoid; imbricated upper teeth, with narrow spatulate crowns that are D-shaped in cross section, and no labial grooves or denticles; nine reduced and un-imbricated lower teeth; asymmetric lower tooth crowns which are elliptical-like in cross section, with lingual grooves and ridges and a lingually bulbous basal crown; a proximal expansion of the humerus that is about 54.9% the length of the humerus; and an ilium with a pointed preacetabular process.
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Other giant eurypterids, particularly the deep- bodied walking forms in the Hibbertopteridae, such as the almost 2-metre-long Hibbertopterus, may have rivalled the pterygotids and other giant arthropods in weight, if not surpassed them. American palaeontologist Alexander Kaiser and South African palaeontologist Jaco Klok suggested in 2008 that the massive size estimates for Jaekelopterus are exaggerated, noting that the size estimates assume that the relative proportions between the chelicerae and body length would stay the same as the animal matured. The denticles (the serrations of the claws) were observed as showing positive allometry (being proportionally larger in larger specimens), which Kaiser and Klok suggest could have occurred in the chelicerae as a whole. Furthermore, the largest coxae (limb segments) found of the same species, measuring wide, suggest a total maximum body length of only .
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Additionally, the mantle edge ofHallaxa chani is semi-translucent and blends in almost seamlessly when spread out on the surface of Halisarca sp. The radular teeth of Hallaxa chani are similar in shape to those of other nudibranchs known to prey primarily on sponges that lack spicules and provided an early clue that Hallaxa chani does not feed on colonial ascidians as originally reported by McDonald & Nybakken (1978) (Goddard, 1981). As noted by Nybakken & McDonald (1981), nudibranchs that specialize on ascidians or fleshy ctenostome bryozoans have a radula dominated by large, paired, wing-shaped lateral teeth. Dorids specializing on dendroceratid and dictyoceratid sponges have thin, comb-like outer lateral teeth with multiple denticles (Goddard, 1981, personal observations; Rudman, 1984; and see electron micrographs of radulae in Gosliner & Johnson, 1994).
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Further subgenera would be named as more differences were noted between the species, such subgenera include Pterygotus (Curviramus) and Pterygotus (Acutiramus), named in 1935 based upon features of the denticles (teeth) of the chelicerae. Pterygotus (Curviramus) was later recognized as synonymous with Pterygotus (Pterygotus) by Leif Størmer the same year, and Erettopterus and Acutiramus would be recognized as separate, but closely related, genera (Erettopterus by Erik N. Kjellesvig-Waering in 1961, and Acutiramus by Størmer in 1974). In 1912, the family Pterygotidae was erected by John Mason Clarke & Rudolf Ruedemann in 1912 to include the eurypterid genera Pterygotus, Slimonia, Hughmilleria and Hastimima. The three latter genera would be reclassified as members of the Hughmilleriidae by Erik N. Kjellesvig-Waering in 1951, leaving Pterygotus and its former subgenera as the sole pterygotid eurypterids.
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The Jenkins' whipray (Pateobatis jenkinsii) is a species of stingray in the family Dasyatidae, with a wide distribution in the Indo-Pacific region from South Africa to the Malay Archipelago to northern Australia. This large species grows to across and has a broad, diamond-shaped pectoral fin disc and a whip-like tail without fin folds. It has a band of heart-shaped dermal denticles running from between the eyes to the tail on its upper surface, along with a characteristic row of large spear-like thorns along the midline. It is uniform yellowish brown above, becoming grayish on the tail past the stinging spine, and white below; there is apparently a spotted color variant that had previously been described as a different species, the dragon stingray (H. draco).
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The first (i), second (2), third (3) and fourth (4) laterals are about equal in shape. The first one is subtriangular, with a slightly concave inner and convex outer margin, thickened at its upper part, the second is very similar, the third is narrower and the fourth is more subquadrangularly elongate; the fifth (5) or last lateral is club-shaped, thickened above, without cusp. Of the uncini (U) the proximal one has a short, broad cusp, with a small denticle near the base of the distal margin; the second is more elongate, also with a small denticle; the subsequent ones are much more elongate, No denticles can be detected, perhaps because the cusps lie so close together, as to cover each other in part.Schepman 1908-1913, The Prosobranchia of the Siboga Expedition; Leyden,E.
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In ants, the most structurally similar cuticular projections can be found throughout most of the body of some species in the formicine genus Echinopla, except on the pygidium, and additionally on the gastral apex of an undescribed species of Strumigenys. Given that these aforementioned taxa are not closely related to Kempfidris, their structures are probably not homologous, but perhaps convergent evolution could be considered, especially in the case of the dacetine ant. Other specialized pygidial structures found in ants are the denticles or spines of Cerapachyinae (now Dorylinae) and the large, upward-curving teeth in Pachycondyla crassinoda workers, but their position and form are very different. Most members of the solenopsidine group are smooth, with little sculpturing, but this species presents a moderate amount of sculpturing on the head, mesosoma, petiole and postpetiole.
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While not true teeth in the usual sense, the dermal denticles of sharks are almost identical in structure and are likely to have the same evolutionary origin. Indeed, teeth appear to have first evolved in sharks, and are not found in the more primitive jawless fish – while lampreys do have tooth-like structures on the tongue, these are in fact, composed of keratin, not of dentine or enamel, and bear no relationship to true teeth. Though "modern" teeth-like structures with dentine and enamel have been found in late conodonts, they are now supposed to have evolved independently of later vertebrates' teeth.nature.com, Fossil scans reveal origins of teeth, 16 October 2013 Living amphibians typically have small teeth, or none at all, since they commonly feed only on soft foods.
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On the other hand, the vomer bones at the front of the mouth were fairly narrow, and the adjacent choanae (holes leading from the nasal cavity to the mouth) were large and close together, as in amniotes. The palate is generally solid bone, with only vestigial interpteryoid vacuities (a pair of holes along the midline) separated by a long and thin cultriform process (the forward branch of the base of the braincase). Apart from the isolated fangs, the palate is also covered with small denticles radiating out from the rear part of the pterygoid bones. Seymouria has a few amniote-like characteristics of the palate, such as the presence of a prong-like branch of the pterygoid (formally known as a transverse flange) as well as an epipterygoid bone which is separate from the pterygoid.
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Morphotype b (MB R 1083 and 1087) teeth had both front to back and side to side curvature, and a D-shaped cross section. Morphotype c (MB R 1090) was curved side to side but not front to back, was not flattened from side to side, had a rounded front with no carina, and bore five strong ridges on its lingual side, but none on its labial flank. Morphotype e (MB R 1092) resembled a typical theropod tooth. It is strongly flattened from side to side, curved from front to back, shows 3 denticles per millimetre (0.04 in), its front carina does not extend to the base of the crown, and there is no ornamentation aside from some weak furrowing of the crown, and two incipient ridges on the lingual side.
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The pectoral fins are short and rounded; the single, small dorsal fin has a rounded margin, and is positioned at the far end of the body, approximately opposite the anal fin. The pelvic and the anal fins are large, broad, and rounded, and are positioned to the tail-end of the frilled shark's body. The very long caudal fin is a triangular tail that has neither a lower lobe nor a ventral notch in the upper lobe, and has a margin equipped with sharp, chisel- shaped dermal denticles, which the shark can enlarge. The underside of the shark's eel-like body features a pair of long, thick folds of skin, separated by a groove, which run the length of the belly; the function of the ventral skin-folds is unknown.
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The mouth is gently arched and contains an anterior row of four and posterior row of two papillae across the floor, which are followed by a seventh papilla in larger individuals. There are 40-42 tooth rows in the upper jaw and 42-46 tooth rows in the lower jaw; the teeth are arranged with a quincunx pattern into pavement-like surfaces. The tail measures three times as long as the disc and bears two long stinging spines on top; after the spine the tail becomes thin and whip-like, without any fin folds. There are numerous flattened, heart-shaped dermal denticles on the back, arranged in a dense central band reaching the base of the tail, and becoming smaller and sparser on the outer portions of the disc.
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Pterygotus would also designated as containing two "subgenera", Pterygotus (Curviramus) and Pterygotus (Acutiramus) in 1935, differentiated by the curvature of the denticles (teeth) of the chelicerae. The same year (1935), Leif Størmer named a new pterygotid genus, Grossopterus, and split Pterygotus into two other subgenera, Pterygotus (Pterygotus) and Pterygotus (Erettopterus), designating Pterygotus (Curviramus) as a junior synonym of Pterygotus (Pterygotus) and not recognizing Pterygotus (Acutiramus). A division into three subgenera of Pterygotus was proposed by Ferdinand Prantl and Alois Přibyl in 1948, retaining P. (Erettopterus) and P. (Pterygotus) but also restoring P. (Acutiramus) to subgenus level. Erik N. Kjellesvig-Waering emended the family in 1951, when the genera Hastimima, Hughmilleria, Grossopterus and Slimonia were referred to their own family, the Hughmilleriidae, which left Pterygotus as the only genus within the Pterygotidae.
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The whip-like tail bears two very slender stinging spines on the upper surface; it is fairly broad and flattened at the base and tapers evenly past the stings. Behind the stings are well-developed dorsal and ventral fin folds; the dorsal fold is smaller than the ventral fold, which is deep and short relative to the tail's total length. The only dermal denticles are four or five small, closely spaced thorns in a midline row behind the spiracles. The upper surface of the disc is yellowish brown, deepening in color towards the margins, with numerous dark orange and light blue spots; the orange spots are smaller, more sharply defined, and densest at the center of the disc, whereas the blue spots are larger, less well defined, and evenly distributed over the disc.
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In Bolton's (1994) key to genera, Megalomyrmex keys in multiple places because of variability in mandibular dentition. Nevertheless, the genus has a distinctive habitus: the antenna is 12-segmented with a 3-segmented club; the general integument is smooth and shiny without coarse sculpture or dull areas; the promesonotum is evenly arched, without promesonotal groove; the propodeum is usually smoothly curved between dorsal and posterior faces, at most with blunt, broad-based tubercles, and never with spines; and the hind tibial spur is simple. In short, the workers look like a Solenopsis with Pheidole antennae. The mandibular dentition varies from a simple set of 5 similar teeth on the masticatory margin, gradually diminishing in size basally, to a condition with 2 large apical teeth followed by up to 12 small denticles.
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These differentiations include the relatively indistinct and symmetrical teeth with moderate serrations (denticles) in Erlikosaurus, and the enlarged serrations in Segnosaurus composed of additional carinae and folded carinae with denticulated front edges, which together created a roughened, shredding surface near the base of the tooth crowns that was apparently unique to Segnosaurus and suggest they consumed unique food resources or used highly specialized feeding strategies, and had a higher degree of oral food processing than other therizinosaurids. In addition to these morphological differences, in 2019 Button and Zanno note that herbivorous dinosaurs followed two main distinct modes of feeding. One of these was processing food in the gut which is characterized by gracile skulls and relatively low bite forces. The second was oral food processing, characterized by features associated with extensive processing such as the lower jaws or dentition.
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Lower jaw of Erlikosaurus (bottom) and Segnosaurus (top) Erlikosaurus lived alongside a larger species of therizinosaurid in the Bayan Shireh Formation, Segnosaurus. In 2016, Zanno and colleagues re-examined the lower jaws and dentition of Segnosaurus making direct comparisons with those of Erlikosaurus in the process. They identified rather complex features in the dentary teeth of Segnosaurus, which are represented by the presence of numerous carinae (cutting edges) and folded carinae with denticulated front edges, and the enlargement of denticles (serrations). These traits together create a roughened, shredding surface near the base of the tooth crowns that was unique to Segnosaurus and suggest it consumed unique food resources or used highly specialized feeding strategies, with the addition of a higher degree of oral food processing than the sympatric—related species that lived in the same area at the same time—Erlikosaurus.
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The possible presence of denticles on the dentary next to the tooth row is particularly significant, as these are present in many tetrapodomorph fish but completely lacking in all but the earliest four- limbed vertebrates, with Elginerpeton believed to have been the last known animal to have possessed such a feature. Overall, Andersonerpeton seems to bridge a gap between stem-tetrapods and aistopods. This classification scheme contrasts with traditional interpretations of aistopods forming a group called Lepospondyli with animals like Diplocaulus and microsaurs, which are almost always considered true crown-tetrapods. However, the idea that aistopods branched off from the tetrapodomorph family tree much earlier than other lepospondyls has been supported by some analyses, such as a 2017 study on the braincase of Lethiscus, which was considered to have been the most "primitive" aistopod prior to the naming of Andersonerpeton.
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The chelicerae of Pterygotus were enlarged, robust and possessed a curved free ramus and denticles of different lengths and sizes, all adaptations that correspond to strong puncturing and grasping abilities in extant scorpions and crustaceans. The IOA values for both Pterygotus and Jaekelopterus match those of high level and active modern predatory arthropods, indicating that they represented visual and active predators. All known pterygotids (though they are so far unknown in Ciurcopterus) possessed cheliceral claws. The first joint of the chelicerae, where it connects to the epistoma (a plate located on the prosoma, or "head"), would have been capable of turning the entire appendage in a twisting way, which has led researchers to conclude that the function of the chelicerae would not have been only, or even primarily, for defense but rather to capture and convey food to the mouth.
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There is also an enlarged "pearl organ" in the middle of the back that is present throughout life, and a row of enlarged denticles (some thorn-like) running from the pearl to the base of the sting. The disc is light gray or brown to dark orange-brown above, with a white to yellow spot just before the eyes and behind the spiracles, and sometimes a subtle, lighter band running around the margin. The underside of the disc is white, and unlike in H. signifer there is a dark (but not black) marginal band that extends from about one-third of the disc length back from the snout top, to the pelvic fins. The tail is gray to orange-brown above and white below at the base, becoming white with dark spots or nearly black past the sting.
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The carinae of the hind edges were also very modified, and bifurcated (split in two) near the cervix, where they formed a flattened triangular, raised facet, which projected from the tooth crown and contacted or approached the folded carinae on the front edge of the crowns behind them (this arrangement is present in teeth 2–12). Such split carinae are known from other tetanuran theropods, where they are considered abnormalities caused by trauma, aberrant tooth replacement, or genetic factors. Though the condition in Segnosaurus was similar, it was uniformly expressed across the teeth of both dentaries, and does not appear to have been an abnormality, but served to roughen the contacts between tooth bases. The 22nd and 23rd dentary teeth of Segnosaurus were significantly smaller than the rest, almost conidont, and had an additional third carina with denticles on their inner sides.
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The horns themselves have a rough, grooved texture that implies they were covered with a keratinous sheath of horn in life, also like ceratopsid horns, and so would have likely been longer than the bony cores indicate. The bones of the skull beneath the horns are unusually thick, and in the larger individuals the bones of roof of the skull (the nasal, prefrontal, frontal and postfrontal) are fused together on each side. Life restoration The teeth of Shringasaurus are low and leaf-shaped (lanceolate) with large denticles on either side, similar in shape to those of Azendohsaurus but lacking the prominent expansion above the root, like the teeth of Pamelaria. Because the skull and jaws are incompletely known, the total tooth count of Shringasaurus is unknown, but like Azendohsaurus it had four teeth in each premaxilla.
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The most recent revision of the genus is that of Schoch & Milner (2014), who list a combination of seven features and two plesiomorphies: (1) nearly circular outline of skull with curved maxilla; (2) prefrontal and postfrontal separated; (3) preorbital region equal to skull table in length; (4) internarial fenestra present; (5) teeth variably monocuspid and bicuspid; (6) vomer with both medial and lateral fangs; (7) palatine lacking denticles; (8) long supratemporal; (9) postparietal longer than tabular. Most of these features are not unique to Tersomius (the combination being unique), as evidenced by the diagnosis of Anderson & Bolt (2013), who list an elongate tabular and a medial curvature of the maxillary arcade at the position of the quadrate (shared with Doleserpeton, T. texensis, and Micropholis) as diagnostic. The poor understanding of T. mosesi often leads it to be excluded in discussion or diagnosing of the genus.
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Life restoration of Teraterpeton, another allokotosaur of previously uncertain placement Azendohsaurus was first misidentified as an ornithischian dinosaur by Dutuit, based on shared characteristics of its teeth such as the leaf-like shape and the number of denticles. It was later believed to be a sauropodomorph instead by other researchers, assigned to the defunct infraorder "Prosauropoda" (then believed to be a distinct monophyletic group related to sauropods, now known to be a paraphyletic grade) based on the morphology of its lower jaw, maxilla and teeth, such as the downward curving dentary and absence of a predentary bone, one of the characteristic traits of ornithischians. These misidentifications were caused by the convergence in jaw and tooth shape between it and the herbivorous dinosaurs while its true phylogenetic relationships could not be realised due to the absence of other bones of the skull and skeleton. The non- dinosaurian identity of Azendohsaurus was first hinted at after the discovery of additional skeletal material recovered from the type locality.
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Siamodon shows a combination of plesiomorphic and apomorphic features, including a maxilla shaped like an isosceles triangle, with the dorsal process located at about mid-length of the bone; a strong longitudinal bulge on the medial surface of the maxilla; at least 25 maxillary teeth, which bear a prominent median primary ridge, and one short weak subsidiary ridge or no subsidiary ridge at all, and mamillated denticles on the crown margins. The maxilla is 230 millimeters long, and has a height of 100 millimeters. The height of the isolated tooth is about 25-28 millimeters, and the width is about 14-17 millimeters. Siamodon differs from more basal iguanodontians, such as Iguanodon and closely related forms, in the morphology of its maxillary teeth, which are narrower and bear a strong median primary ridge, sometimes accompanied by a weak subsidiary ridge, instead of a distally displaced primary ridge and several subsidiary ridges, and the apex of the maxilla is in a more posterior position.
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Trematopids have typically been identified by the presence of a noticeably enlarged naris that is often sub-divided in Permian forms such as Acheloma. They are also among the largest of the dissorophoids, with some specimens of Acheloma exceeding 18 cm in skull length and thus being rivaled only by middle Permian dissorophids such as Anakamacops. Schoch & Milner (2014) diagnosed trematopids by the following features: (1) greatly expanded naris replacing much of the lacrimal; (2) medially situated narial flange meeting antorbital bar; (3) otic notch with a ventral margin sloping at less than 45-degrees in large individuals; (4) a medial inflection of the rim of the adductor fossa; (5) a pterygoid-vomer contact; (6) a triangular patch of denticles on the basal plate of the parasphenoid; and (7) a humerus with a supinator process. Milner (2018) further refined this based on his restudy of Mordex, including only characters 1, 3, and 5 from Schoch & Milner (2014), noting that some typical trematopid features are either not known or are not present in the primitive Mattauschia and Mordex.
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Eriocephalus africanus, showing lightly arachnoid leaves, and heavily arachnoid seed follicles. The arachnoid leaves of this Gazania are covered with a fragile cobwebby felt Hayworthia arachnoidea - inaccurately named the "cobweb aloe" - Its spidery appearance arises from the long denticles on its leaf margins Cephalocereus senilis is an example of a long-lasting, robust arachnoid effect created by modified spines Arachnoid as a descriptive term in botany, refers to organs such as leaves or stems that have an external appearance similar to cobwebs from being covered with fine white hairs, usually tangled. Such material is one common cause of plants having a grey or white appearance.Jackson, Benjamin, Daydon; A Glossary of Botanic Terms with their Derivation and Accent; Published by Gerald Duckworth & Co. London, 4th ed 1928 The usages of various authors in distinguishing between "arachnoid" and a few other terms referring to hairiness, such as floccose, pubescent, tomentum, cottony, or villous, tend to be arbitrary, but as a rule the term is best reserved for hairiness lighter than a felted layer, and inclined to rub off or to be easily damaged in other ways.
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This assignment was based on five characteristics, all present in Eolambia: the presence of denticles on the premaxilla; the quadrate's narrow joint with the lower jaw; the narrow dentary teeth; the presence of a single edge, or carina, on each dentary tooth; and the angled deltopectoral crest on the humerus. Caudal vertebrae of Eolambia; note the tall neural spines Within the Hadrosauridae, Kirkland further considered Eolambia to either be a basal member of the Lambeosaurinae, or the sister group of Lambeosaurinae. He identified five characteristics shared with the Lambeosaurinae, as defined across various studies: the absence of a foramen on the premaxilla; the (at least partial) enclosure of the nostril by the premaxilla; the development of a shelf on the maxilla; the very tall neural spines of the caudal vertebrae; the robustness of the humerus; and the large "boot" of the ischium in adults. Kirkland found that two additional traits separated the crestless Eolambia from other, crested lambeosaurines, which were considered as being related to the development of the crest: the elevation of the nasal cavity above the eye socket, and the shortening of the parietal.
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