One of the preserved unguals is larger than the others, and it may represent the claw of the first finger. Other unguals are as large as each other, indicating that the second and third fingers had claws of equal size. The deep unguals of similar shape differs from the condition in other early therizinosauroids, which have longer unguals which differ in shape between different fingers.
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Photographs Right foot of Nothronychus graffami The manual unguals (claws) are proportionally larger than the phalanges, strongly flattened from side to side, and recurved with more degrees of specialization than therizinosauroids. Most therizinosaurids had sharply pointed and recurved unguals with very robust tubercles (flexor tendons attachment). These traits are better seen on Nothronychus and Segnosaurus. In Therizinosaurus, however, the manual unguals were extremely elongated and straight with poor curves.
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Metatarsals III and IV were almost equal in size, the second was slightly narrow and the first one was the shortest. There are, however, traces of metatarsal V but it is highly reduced and has no functional significance−as seen on Segnosaurus. The phalangeal formula was as in other maniraptorans, IV-4, III-3, II-2 and I-1 (excluding the unguals). The pedal unguals were sharply pointed, side to side flattened and smaller than the manual unguals.
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Unguals were low and wide, a "hoof"-like appearance also seen in Silesaurus and the unrelated shuvosaurids.
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The phalangeal formula is probably 2, 3, 3, 4, 3 (including the unguals, which are strongly curved and arched).
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The unguals of digits II and IV are asymmetrical, with more elongated inner and lateral flanges, and longer upper regions.
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Megaraptor retained a vestigial fourth metacarpal, the hand bone that would have connected to the fourth finger in early dinosaurs. This was a primitive feature lost by most other tetanurans. The first two fingers had absurdly large unguals (claws); in Megaraptor the first claw was larger than the entire ulna. Unlike the large unguals of many other theropods (megalosauroids, for example), megaraptoran claws were thin and oval-shaped in cross-section.
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It also presents truncated unguals, characteristics otherwise unknown in the Sauropoda. This parallels the vertical position of the metacarpals and the finger reduction in the hand of other titanosaurs.
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It also includes well-preserved manual unguals. Manual and pedal morphology show that the specimen is distinct from other theropods from the Cedar Mountain Formation and from other previously described therizinosauroids.
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The use of the giant recurved manual unguals of spinosaurs is still under debate; suggested functions have ranged from gaffing aquatic prey out of the water, to scavenging carcasses or digging.
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They possessed unbent and flattened unguals, suggesting they were diggers. It is uncertain whether their digging unguals were adapted for burrowing or solely digging for food. Many varanopseids were arboreal, however the well-developed olecranon(bony prominence of the elbow) of Mesenosaurus indicates the presence of triceps and anconeus muscle, both of which would provide powerful forearm extension. This forearm extension strength combined with its somewhat small/medium body size supports the idea of a burrowing lifestyle.
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This is mainly due to their elongated unguals. which have a narrow attachment groove along their length and are quite strongly arched. It is not known what benefit these specialised features conferred.
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The horned triangular head of Leptopleuron, as well as an overbite comparable to the horned sand lizard, were evident of its burrowing lifestyle. With an overbite aiding in less ingestion of dirt, along with spade-like unguals and strong limbs for efficient digging, Leptopleuron was likened to today's burrowers of Phrynosoma, a genus consisting of horned lizards. Skepticism remains, however, due to both its manus and pes having slender phalanges and unguals compared to Procolophon, which is characteristically inefficient for dredging through dirt.
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Phytosaurs and aetosaurs also share a knob-like attachment point midway down the fibula, so it is unclear whether the case in ornithosuchids is a unique case of convergent evolution, or alternatively the retention of a trait independently lost by several archosaur lineages. Unlike most other early archosaurs, the pedal unguals (the distalmost bones of the feet that form claws) are laterally compressed. They are sharp and recurved. The unguals are very deep, being taller than they are long, especially on the inner digits.
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It had three fingers, which were similarly developed; the first (the "thumb") was the strongest, the third was the weakest and the second was the longest. The unguals (claw bones) were strong, somewhat curved (that of the first finger was most curved) and compressed sideways with a deep groove on each side. The unguals were similarly developed, though the third was slightly smaller. The pubis (pubic bone) was long and slender, ending in a pubic boot which expanded to the front and back, a general feature of ornithomimosaurs.
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The foot of Goyocephale is partially preserved, and at least three digits (digits II, III and IV) were present. On each toe, the unguals are triangular but not recurved, with the ungulate of the third toe being the largest.
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The manus, hand, is composed of freely articulating metacarpals, with well-formed phalanges and unguals on the first and second digits. The thorax is closed at the underside, by gastralia. The pelvis has a footed pubis.O'Connor, J. and Dyke, G. (2010).
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The upper articulation is symmetrical and has a cross-ridge that divides the surface into two asymmetrical parts. The size of the unguals IGM 100/16 and 100/17 may indicate that they belong to manual digits I and III, respectively.
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The second metacarpal is longer, and the third and fourth are tied for the longest bones of the hand. Unguals (claws) have not been found, and the rounded ends of certain phalanges indicates that Vancleavea likely did not possess them.
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The hindlimbs are relatively elongated, a trait also mentioned by Holtz. The femur is slender with a distinct head and neck, measuring . The pes is robust with large and strongly curved pedal unguals. No direct evidence of feathers was preserved with the skeleton, but Xu et al.
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They closely resembled modern tinamous. They possessed a rhynchokinetic skull with relatively unfused cranial bones, a weakly fused pygostyle and a splenial. The unguals were more curved than in tinamous and probably allowed better perching in trees. The order Lithornithiformes was erected by Dr. Peter Houde in 1988.
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Reconstructed skull, BYU For instance, some elements were wrongly referred to the genus; the lacrimal bone of the specimen CEU 184v.83 turned out to be a postorbital from the ankylosaur Gastonia. Britt et al. also suggested that the previously identified manual unguals of the specimens CEU 184v.
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Of the two manual unguals (claws) referred to Cristatusaurus, one was equivalent in size to those found for Suchomimus and Baryonyx, while the other was about 25 to 30 percent smaller. As a spinosaur, it would have wielded these claws with three-fingered hands carried by robust arms.
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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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Phuwiangvenator ("hunter of Phu Wiang") is a genus of megaraptoran theropod that lived during the Early Cretaceous period in what is now Thailand. It contains a single species, P. yaemniyomi, recovered from the Sao Khua Formation. The holotype was first found in 1993, before being named in 2019.. The holotype specimen consists of a partial skeleton consisting of a dorsal vertebra, three fused sacral vertebrae, right metacarpal II, right manual phalanges and unguals, right and left tibiae, left astragalocalcaneum, left metatarsal I, right metatarsals II–IV, right pedal phalanges and unguals, with a referred specimen including an atlantal intercentrum and right astragalocalcaneum which were found together. In the phylogenetic analyses it was found to be the basalmost megaraptoran.
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The third metacarpal bone is the same length as the second but 68% narrower. The phalanges (finger bones) are long and robust, the longest being the first phalanx about 72% longer than the second metacarpal, and the third phalanx is the smallest. The unguals (claws) are weakly curved, and decrease in size and curvature from first to third finger.
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Cretaceous-aged dinosaur fossil localities of Mongolia; Therizinosaurus fossils have been collected from the Altan Uul, Hermiin Tsav, and Nemegt localities at the area A (Nemegt Formation localities) The first fossil remains of Therizinosaurus were discovered in 1948 by the Mongolian Paleontological Expedition of the USSR Academy of Sciences at the Nemegt Formation of the Gobi Desert, southwestern Mongolia. The expedition unearthed enormous manual unguals (claws) from the stratotype locality, Nemegt. This unusual specimen was labelled under the number of PIN 551-483 and consisted of three partial manual unguals, a metacarpal fragment and several rib fragments. Later on, the fossils were named and described by the Russian paleontologist Evgeny Maleev in 1954, who thought they belonged to a large, long marine turtle that used the giant claws to harvest seaweed.
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The position of the fossil suggests Cabarzia had a fifth toe which was angled relative to the rest of the foot. One of the most clear differences between Cabarzia and Mesenosaurus was the fact that Mesenosaurus had long but rather straight unguals while those of Cabarzia were shorter, deeper, and sharply curved, a characteristic also known in the hands of Tambacarnifex.
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The first metatarsal is short and broad but the other four are long and flat, although they are broken so it is hard to say exactly how long. The toes have, respectively, 2,3,4,5 and 4 phalanges. These all narrow as they head towards the claws. The unguals are all very large and broad, and have rounded ends without a recurve.
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Two lower phalanges belong to digit IV. These phalanges are even more flattened than phalanx II-2. Their lower and upper surfaces are similar to those of phalanx II-2, but can be differentiated in being more concave. Pedal unguals are mostly flattened and convex with elliptical upper surfaces. These elements are more arrow-shaped and more sharply developed than in hadrosaurids.
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Holotype right foot of Erlikosaurus with unguals removed Body remains of Erlikosaurus are very sparse compared to the cranial elements, consisting of a humerus, a right foot and some cervical vertebrae. The particular cervicals were not figured and counted but briefly described. The cervicals are platycoelus (slightly concave at both ends) with low neural arches. Being relatively robust, they have thick prezygapophyses and large parapophyses.
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Males have black and white feathers while the female has grayish brown feathers. They are unique among birds in that they retain only the third and fourth toe on each foot. Ostrich wings have claws, or unguals, on the first and second fingers (and, in some individuals, also on the third). Ostriches differ from other paleognathes in that they have a reduced vomer bone of the skull.
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Each hand had four fingers, with no thumb (first finger). The index (second), third, and fourth fingers were approximately the same length and were united in life within a fleshy covering. Although the second and third finger had hoof-like unguals, these bones were also within the skin and not apparent from the outside. The little finger diverged from the other three and was much shorter.
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The unguals of the foot are less curved than in Eomaia or Sinodelphys, indicating that the mammal could climb but less effectively than in the two latter genera.Larsson, Hans, Hone, David, Dececchi, T. Alexander, Sullivan, Corwin, Xu, Xing. "THE WINGED NON-AVIAN DINOSAUR MICRORAPTOR FED ON MAMMALS: IMPLICATIONS FOR THE JEHOL BIOTA ECOSYSTEM" "Program and Abstracts. 70th Anniversary Meeting Society of Vertebrate Paleontology October 2010" 114A.
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Unlike Struthiomimus, the anterior portion of the ilium reaches as far forward as the end of the pubic shaft, and the medial (inner) edge of the third metatarsal is straighter as well. Compared to Ornithomimus, the antorbital fenestra is proportionally shorter. Finally, Rativates is smaller than the large Dinosaur Park ornithomimid (still unnamed as of 2016), and also differs in the anatomy of its unguals (foot claws).
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The holotype also had very large and flat manual unguals (hand claws), which played a role in its initial classification as a dromaeosaurid (as the hand claws were mistaken for foot claws) as well as its current classification as a megaraptoran. An astragalus (NMV P150070) found in Australia, provisionally referred to Australovenator, may belong to a megaraptoran more closely related to Fukuiraptor due to being very similar to it.
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The third metatarsal has an only weakly developed ginglymoid inferior articular surface. The unguals, the bones of the foot claws, are narrow and asymmetric with shallow grooves on both sides. The foot claws have only a shallow a longitudinal groove for the flexor tendon, but a deep groove in the lower inner side near the surface of the articulation. Tototlmimus shows a foot with a typical build for ornithomimosaurs.
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The femur measures , it is lightly curved and has a large head; the fourth trochanter is fragile and place above the midlength of the femoral end. Being larger than the femur, the tibia measures and its proximal articulation is more developed than distally. The right pes is virtually complete, only lacking the distal end of the IV metatarsal. The pedal unguals are dorsoventrally flattened and somewhat sharply-developed.
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Unlike most pseudosuchians, poposauroids lack bony scutes known as osteoderms. The only exception to this is Qianosuchus, which possessed numerous tiny osteoderms, lying in a row extending down the neck and body. In all poposauroids, the tip of the fibula (outer shin bone) is symmetrical and straight when seen from the side, rather than slanted as in other non- crocodylomorph pseudosuchians. Poposauroids more advanced than ctenosauriscids had flattened, "hoof-like" pedal unguals (toe claws).
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The pedal digits are very peculiar in structure; the first digit is reduced in length, with all the remaining digits being nearly equal in length, however the fourth digit is very thin compared to the others. The phalanges of the three first digits are shortened, robust with comparable structure. The second and third phalanx of fourth digit are discoidal and stocky. Lastly, the unguals are recurved, exceptionally large, and strongly flattened laterally.
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Carodnia is characterized by bilophodontA loph is a crest on the crown of a tooth. A bilophodont tooth has two parallel lophs running transversally across the tooth. first and second molars and more complex lophate third molars, which suggests possible links to pyrotheres, uintatheres, and even arctocyonids. The bones of the foot are short and robust and the digits terminate in broad, flat, and unfissured hoof-like unguals, unlike any other known meridiungulate.
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The top border of this crest is very pointed and thick; it likely served as the site for attachment of the extensor tendons in life. The lower heads are nearly symmetrical, but the central fossa is considerably wider and deeper in the first phalanx. The preserved unguals are specially enormous, estimated to be approximately in length. Unlike other therizinosaurs, they are very straight, laterally flattened and not particularly curved with very sharp point tips.
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Life restoration by Nobu Tamura Dineobellator was around in length and is believed to have weighed about . Unique features of the skeleton suggest greater hand and feet flexion than normal for dromaeosaurs, a tighter grip strength in the manual unguals, and greater movement at the tail base. These may aid in agility and predation. Additionally, the presence of quill knobs on the ulna suggest it was feathered, as assumed for all dromaeosaurids.
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The first and fourth metacarpals were short, while the second was slightly longer than the third. The metacarpus and especially the first phalanges were proportionally very short, unlike in most other basal theropods. Only the first phalanges of digits II, III, and IV are preserved in the holotype; the total number of phalanges and unguals (claw bones) is unknown. The anatomy of metacarpal I indicates that phalanges had originally been present on this digit, as well.
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On the other hand, the unguals (claws) were long and sharply pointed, with robust flexor tubercules (tendon attachment bumps). Some of the hip bones were obscured by the rest of the skeleton, but the ischium (front lower plate) was longer than the pubis (rear lower plate). The femur (thigh bone) was twisted, with the knee joints offset at 45 degrees from the rest of the shaft. In other early reptiles, this angle of torsion was smaller, usually 10 to 30 degrees.
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Sinornis is a genus of enantiornithean birds from the Lower Cretaceous Jiufotang Formation of the People's Republic of China. When it was described in 1992, this 120 million-year-old sparrow-sized skeleton represented a new avian sharing "primitive" features with Archaeopteryx as well as showing traits of modern birds. Its basal features include, but are not limited to, a flexible manus with unguals, a footed pubis, and stomach ribs. Sinornis is known only from the type species, Sinornis santensis.
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Excavation of the right hindlimb of A. olseni specimen AMNH 6554, in 1923. George Olsen on the right In 1923, the Third Asiatic Expedition of the American Museum of Natural History, led by chief paleontologist Walter W. Granger was hunting for dinosaur fossils in Mongolia. On April 25, assistant paleontologist George Olsen excavated and recovered the holotype AMNH 6554, a nearly complete right hindlimb. This included a virtually complete right hindlimb with some elements from the left pes and two manual unguals.
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294, BYU 9438 and BYU 13068 are indeed pedal unguals. This suggestion was confirmed by Senter in 2007. According to Kirkland et al. in 1993, Utahraptor can be recognised by the following autapomorphies: claws on the hand that are more specialized as cutting blades than in other dromaeosaurids; a lacrimal bone with distinctly parallel mesial and outer sides, giving it an elongate subrectangular appearance in top view; and a base of nasal opening on the premaxilla parallel to the premaxillary tooth row.
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Longusunguis was first described and named by Min Wang, Zhong-He Zhou, Jingmai K. O'Connor and Nikita V. Zelenkov in 2014 and the type species is Longusunguis kurochkini. The generic name is derived from the Latin words longus, meaning "long", and unguis, meaning "claw", in reference to the distinctly elongated pedal unguals that this taxon shares with other bohaiornithids. The specific name, kurochkini, honors the late Prof. Evgeny Kurochkin, a prominent paleontologist, for his contributions to the study of fossil birds.
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The upper half of the femur was triangular in cross section, a feature shared with Masiakasaurus. The metatarsals of the three weight-bearing toes were arranged in an arc, with the fourth metatarsal straight and adhering tightly to the third for its entire length; these features are unique to Limusaurus. The hallux (the first toe or dewclaw) was reduced, being only 17% the length of the third metatarsal, another unique feature. As in other ceratosaurians, the unguals of the foot had two grooves on their sides.
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Overall, it closely resembled the humerus of araeoscelidian reptiles such as Petrolacosaurus and Araeoscelis. The hand had five digits, with elongated phalanges (finger bones). The phalangeal formula (number of phalanges in each finger) was 2-3-4-5-4, meaning that the fifth finger had one more joint than that of generalized reptiles (which have a phalangeal formula of 2-3-4-5-3). The phalanges also increase in length towards the tip of the fingers, where they abut large, strongly curved unguals (claws).
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The humerus (forearm bone) is flat and irregularly shaped, similar to the "L-shaped" humeri of most early tetrapods and stem-tetrapods (particularly Baphetes), but not the thinner, hourglass-shaped humeri of temnospondyls and amniote relatives. The ulna and radius (lower arm bones) are short and tubular, with the ulna being longer and having a moderately developed olecranon process. The hands are not complete in any specimen, but triangular unguals ("claw" bones) were present. Only the holotype specimen preserves the rear half of the torso.
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The lower half of the third metatarsal was broad when viewed end on, partly covering the adjoining two metatarsals to each side, but narrowed abruptly at mid-length, wedging between those bones and disappearing (an arctometatarsalian foot structure). The third toe was proportionally shorter in relation to the limb than in other ornithomimids. As in other ornithomimids, the foot had no hallux (or dewclaw, the first toe of most other theropods). The unguals of the toes were flat on their lower sides; the outer two declined slightly outwards from their digits.
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The non-terminal manual phalanges are about as long as wide and lack any constriction between the articular ends, and manual unguals are reduced. It is these reduced limb proportions that demonstrate Eoabelisaurus was indeed a primitive abelisaurid. The exact number of vertebrae is unknown due to several gaps in the holotype's spine, but its cervical vertebrae are short and have two pneumatic foramina on either side of the centra. The length of vertebral centra remains constant over the preserved portion of the tail, but middle and posterior caudals are considerably lower.
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Therizinosauridae (meaning scythe lizards) is a family of derived (advanced) therizinosauroid dinosaurs whose fossil remains have been found in mostly Late Cretaceous boundary. Even though representative fossils have only been found throughout Asia and North America, the range of Therizinosauridae is believed to have spanned much of the supercontinent of Laurasia based on several footprints and isolated remains on Europe and Africa. Therizinosauridae compromises currently seven described and named taxa. Therizinosauridae was named in 1954 by the Evgeny Maleev after the large, claw-bearing unguals of the type species Therizinosaurus cheloniformis.
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Certain features of their hands indicate that they were paddle-like in shape and structure, being used to swim in a manner much similar to that of modern turtles.Markus Lambertz et al, A caseian point for the evolution of a diaphragm homologue among the earliest synapsids, Annals of the New York Academy of Sciences (2016). DOI: 10.1111/nyas.13264 Their digits were believed to have a considerable range of motion and large retractor processes on the ventral surfaces of the unguals allowed them to flex their claws with powerful motions.
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Metatarsal II is straight, with a flattened proximal portion and boxy distal portion. Metatarsal IV has a more irregularly-shaped distal portion but is also straight, an unusual feature more akin to Lagerpeton and pterosaurs rather than the more curved bone of other dinosaurs. Isolated phalanges are variable in proportions, with one having a wide proximal articulation and the rest having tall, triangular proximal articulations and more well-developed joint surfaces. Unguals are triangular in cross section and curved, though not to the extent seen in more advanced theropods.
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While the lack of strong compression of the toe unguals distinguished Segnosaurus from Erlikosaurus from the same formation, the lack of compression was common among therizinosaurs and therefore not unique to Segnosaurus. The cervical vertebrae were platycoelous and had large, massive centra (bodies) and low neural arches. The sacrum consisted of six, firmly fused vertebrae; the centra of these vertebrae were broadened and relatively elongated, and each centrum was slightly longer than their width. The neural spines here were not very long but surpassed the level of the ilia.
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The pelvic girdle of Achillobator features plesiomorphic (primitive) saurischian characteristics compared to other dromaeosaurids. For instance, the pubis is aligned vertically and has a relatively large pubic boot (a wide expansion at the end), unlike most other dromaeosaurids, where there is generally a much smaller boot. The preserved vertebrae are very robust and features a series of pleurocoels. The above differences led Burnham and team in 2000 to suggest that the holotype of Achillobator in fact, represents a paleontological chimera, and only the pedal unguals may have come from a dromaeosaurid-grade dinosaur.
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Eusauporoda are also hypothesized to have a semi-digitigrade foot posturem demonstrated by footprint evidence. Paleontologist Jeffrey Wilson explains that eusauropods differ from theropods and prosauropods that have digitigrade pes where their heel and metatarsals are lifted off the ground. Eusauropods show asymmetry in their metatarsal shaft diameters where metatarsal I is broader than the others, suggesting that their weight was mostly assumed by their inner feet. According to Steven Salisbury and Jay Nair, basal eusauropods retain four pedal unguals but reduce their phalangeal number in their fourth digit to three units.
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The osteoderms are strongly robust, most spine-shaped osteoderms measured in height. MPC-D 100/1355 was found in association with a partial halfring, as well as other body elements. Only the left manus is preserved, it is virtually complete preserving five digits, only lacking some unguals and phalanges. The preserved left pes is very unique; it was described as having four digits, this statement however, was proved to be a product of the initial skeleton mount and three digits is more accurate/likely, as seen in related ankylosaurines.
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The sequence gradually shallows upwards with the terminal Hakobuchi Formation representing a fluvial-inner shelf environment. Numerous fossils are known from the unit, mostly ammonites and bivalves, but also marine vertebrates such as mosasaurs and marine turtles. Dinosaur remains are among the fossils that have been recovered from the group, including those of an indeterminate maniraptoran consisting of a right metacarpal and manual unguals from the Early Campanian Osoushinai Formation from northern Hokkaido. Nipponosaurus, which is known from an unnamed unit of the group from Southern Sakhalin probably late Santonian or early Campanian in age.
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This contrasts with the hands of other reptiles where first and fifth digits are spread out from each other and the fourth digit is the longest. The metatarsals and digits of the foot also diverge in a smooth arc, but unlike the hand they are not symmetrical, with a long fourth toe and a short, hooked fifth digit. All the digits of the hands and feet are unusually short for an archosauromorph, contrasting with the related Trilophosaurus. The claws (or unguals) are all very large, narrow and sharply recurved, and are significantly larger than the preceding finger bone they were attached to.
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Contrary to Maleev, he illustrated the three holotypic manual unguals and reidentified the metacarpal fragment as a metatarsal. The unusual shape of both metatarsal and ribs fragments led Rozhdestvensky to classify them as sauropod remains. Further expeditions in the Nemegt Formation unearthed more fossils of this particular genus. In 1968, prior to Rozhdestvensky statements, the upper portion of a manual ungual was found in the Altan Uul locality and labelled as IGM 100/17. Another fragmented ungual was discovered at the Hermiin Tsav locality in 1972; this specimen, IGM 100/16, was found preserving its lower portion.
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The skeleton was found in the Jiufotang Formation at Liaoning, People's Republic of China. The skeleton exhibits remarkable basal features shared with Archaeopteryx, a genus of early bird that is transitional between older feathered dinosaurs and modern birds. Until the discovery of Sinornis scientists did not know much about the evolution of flight that lead to modern birds because Archaeopteryx, which lived in the Late Jurassic period around 150 million years ago, lacks many of the modern flight and perching of modern birds. Some of the primitive features found in Sinornis include moderately recurved manual unguals, as opposed to the high-recurved one in Archaeopteryx.
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All specimens of Barasaurus as well as Procolophon share the presence of the medial flange on the proximal end of the first metatarsal, a possible synapomorphy for Procolophonoidea. All specimens of Barasaurus are distinguished from all other procolophonians by the presence of a pedal centrale and relatively short pedal unguals, and therefore these represent two additional autapomorphic reversals of Barasaurus. Although the complete pedal phalangeal count of Barasaurus is unknown from the holotype, the lower Triassic material revealed that the phalangeal formula for this genus is 2:3:4:5:5. Procolophonoid material with such arrangement is otherwise known from the Lower Sakamena Formation.
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Comparison between Carnotaurus, Dilophosaurus, and Eoabelisaurus forelimbs demonstrating gradual reduction starting at the distal elements Before the discovery of Eoabelisaurus, abelisaurid anatomy was only known from a handful of Late Cretaceous taxa that were aberrant in their morphology, such as their unusual skull structure and reduction of their forelimbs. Eoabelisaurus shows what was previously an unknown stage in the evolution of abelisaurids, having only some of the cranial modifications and a unique combination of features in its forelimbs. The manus of Eoabelisaurus have a derived morphology, with short and robust metacarpals, non-terminal phalanges, and reduced manual unguals. The humerus is unreduced, and the ulna and radius are shortened but do not differ from more basal ceratosaurs.
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Ungual and phalanx of AMNH 6368 that were later confirmed to pertain to some therizinosaur and not Alectrosaurus In 1933, Charles Gilmore examined the available material and concluded that AMNH 6554 and AMNH 6368 were syntypes belonging to the same genus. He based this on his observation that the manual unguals from both specimens were morphologically similar. Observing similarities with the hindlimbs of specimen AMNH 5664 Gorgosaurus sternbergi, he classified this new genus as a "Deinodont", a term that is now considered equivalent to tyrannosaurid. Due to its fragmentary nature, there is presently very little confidence in restoring its relationships with other tyrannosauroids and many recent cladistic analyses have omitted it altogether.
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During the same year and also from Hermiin Tsav, the specimen IGM 100/45 was discovered by the Joint Soviet- Mongolian Paleontological Expedition. Unlike the previous findings, this specimen is represented by a hindlimb composed of a very fragmented femur with tibia, astragalus, calcaneum, a lower tarsal, a tetradacyl pes compromising four partial metatarsals, nearly complete digits I, II and IV (although II and IV are missing the unguals) and the presumed second phalanx from the digit III. These newer remains were described by the also Mongolian paleontologist Altangerel Perle in 1982. He referred the specimen to Therizinosaurus based on the striking resemblance to Segnosaurus, another therizinosaurid genus also known from limb elements.
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The holotype, ML 357, a partial skeleton lacking the skull, consists of two maxillary teeth, three caudal centra, one chevron, a distal epiphysis of right humerus, one manual phalanx, three manual unguals, a distal epiphysis of the right femur, the proximal and distal epiphyses of the tibia and fibula, an astragalus, a calcanaeum, three tarsals, four metatarsals and pedal phalanges. It was in 1991 found at Vale de Frades by Carlos Anunciação of the Museu da Lourinhã, in layers of the Bombarral Unit dating to the Tithonian. Histology shows that the holotype specimen was between 27 and 31 years old. A left femur (ML 434), found near Praia do Caniçal, has been referred to this taxon.
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It consists of a partial, sub-adult, skeleton that is largely disarticulated. A significant number of fossilized bones were recovered, including: cranial fragments, a mandible, teeth, three cervical vertebrae, four dorsal vertebrae, four dorsal ribs, two sacral vertebrae, twenty-five caudal vertebrae with a pygostyle, three chevrons, an incomplete furcula and scapula, both coracoids, both forelimbs, both ilia, an incomplete pubis, an incomplete ischium, a femur, both tibiae (one incomplete), an incomplete fibula, the astragalus and calcaneum, several tarsals, metatarsals, manual and pedal unguals, and skin impressions of the primitive plumage. The pelvic girdle and caudal vertebrae were discovered during a re-excavation of the fossil quarry were the first elements of the holotype were found. These rediscovered elements helped to complete the holotype specimen.
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It includes the (lower jaws), an incomplete , a complete and (lower arm bones), of the fingers, a forelimb (claw bone), an almost-complete , an incomplete right , six , ten from the front of the tail, fifteen from the hindmost part of the tail, the first , and fragments of the dorsal ribs. Two more specimens were designated as paratype specimens; specimen IGM 100/82 from the Khara Khutul locality includes a femur, and (leg bones), and , five toe phalanges including a foot ungual, rib fragments, complete , the upper portion of an , and the lower portion of a . Specimen IGM 100/83 includes a left (shoulder girdle), a radius, an ulna, forelimb unguals, and a fragment of a (neck) vertebra. In 1980, Perle and the paleontologist Rinchen Barsbold assigned another specimen to Segnosaurus; IGM 100/81 from the Amtgay locality included a left tibia and fibula. In 1983, Barsbold listed additional specimens GIN 100/87 and 100/88.
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Fossil localities in Mongolia. Locality of Achillobator in Burkhant, at Area D In 1989, during a field exploration conducted by the Mongolian and Russian Paleontological Expedition in the Gobi Desert, examining the outcrops at Khongil, South Central Mongolia, many dinosaur fossil discoveries were made. About 5.6 km away from the Khongil locality, a large and mostly disarticulated partial theropod skeleton was discovered in fine-grained, medium sandstone/gray mudstone that was deposited dating back to the Late Cretaceous epoch at the Burkhant locality, Bayan Shireh Formation. The preserved specimen was found in association with a left maxilla preserving nine teeth and two alveoli, four cervical vertebrae, three dorsal vertebrae and eight caudal vertebrae, a nearly complete pelvic girdle compromising both pubes, right illium and right ischium, both femora and left tibia, left metatarsals III and IV, manual and pedal phalanges with some unguals, right scapulocoracoid, an isolated radius, two ribs and caudal chevrons.
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More recently, Mike Taylor and Matt Wedel suggested that the whole neck would be 2.9 times the size of the humerus, which was , resulting in a long neck based on comparisons with the cervical vertebrae series of Nanshiungosaurus. Life restoration Therizinosaurus can be distinguished from other therizinosaurids in having very straight manual unguals that are side to side compressed (flattened) and hypertrophied (elongated) with poor curves, an extended deltopectoral crest on the humerus, the length of metacarpal I is larger than 2/3 the length of metacarpal III, and the metacarpal I has an enlarged inner crest that connects the inner lower condyle and upper inner lobe. The most distinctive feature of Therizinosaurus was the presence of gigantic claws on each of the three digits of its front limbs. These were common among therizinosaurs but particularly large and stiff in Therizinosaurus, and they are considered as the longest known from any terrestrial animal.
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However, in 2007 these were described by paleontologist Martin Kundrát and colleagues and tentatively identified as therizinosaurids based on anatomical features such as the tooth-less premaxilla with a downturned edge, dentary with a lateral shelf, teeth with leaf-shaped crowns, humerus with a prominent deltopectoral crest, ilium with an expanded anterior end, and the elongated, sharply-pointed manual unguals. Most eggs have an average size of and given these dimensions, they likely were laid by a medium- sized female. Although several egg clutches were found, one was found containing 7 eggs of which 3 of them were preserving the embryos. In 2019, Hartman and colleagues were the first authors to include these embryos in a phylogenetic analysis and as expected, the embryos were recovered as therizinosaurids. In a 2013 conference abstract, paleontologist Yoshitsugu Kobayashi and colleagues reported an exceptional nesting ground site of theropod dinosaurs at the Javkhlant Formation, which contained at least 17 egg clutches from the same layer within an area of 22 m by 52 m.
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Close up of the skull According to Pu et al. 2013, Jianchangosaurus can be distinguished based on the presence of 27 tightly packed maxillary teeth; the dorsal border of the antorbital fenestra is formed by the maxilla, nasal, and lacrimal, but with the majority of the border formed by the nasal; there is no participation of jugal in the margin of the antorbital fenestra; a short diastema is present in the anterior tip of the dentary; dentary teeth have a concave labial surface and a convex lingual surface (this condition is present for all except six anterior teeth); the lack of prominent hypapophyses in the anterior dorsal vertebrae; the anterior caudal centra have an oval cross section and the articular facet is as tall as it is wide; the presence of weakly curved manual unguals with weak flexor tubercles positioned ventral to the articular facet; the ilium is shallow and elongated; the ridge bounding the cuppedicus fossa is confluent with acetabular rim; and there is extensive contact between the pubic apron.
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Holotype skull The holotype, AR-1/10, represents a disarticulated partial skeleton spread over an area of seven by three meters. It consists of a nearly complete skull, isolated left and right nasals, a dentary fragment, 15 isolated teeth, an atlas, five cervical vertebrae, two cervical ribs, possibly the first and seven more posterior dorsal vertebrae, a section of synsacrum, three isolated dorsal ribs, seven dorsal rib fragments, three caudal vertebrae, four chevrons, a coracoid with a small portion of the scapula, a scapular blade fragment, two xiphosternal plates, both partial humeri, right articulated ilium, ischium and pubis, left articulated ischium and pubis, and 70 osteoderms. The second partial skeleton AR-1/31, designed as the paratype, consists of a partial left jaw with dentary and surangular and isolated angular, ten teeth, five cervical, nine dorsal, three or four dorsosacral, one caudosacral and 14 caudal vertebrae, a sacrum, two sacral rib fragments, both ischia with fused pubes, two left ilium fragments, complete right ilium, femur, tibia and fibula, a calcaneum, four metatarsals, eight phalanges, nine unguals, and 90 osteoderms.
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