The myelencephalon or afterbrain is the most posterior region of the embryonic hindbrain, from which the medulla oblongata develops.
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Ventrals rounded at sides, subcaudals paired (divided). Maxillary teeth 20–25, subequal, except for the 3-5 most posterior, which are slightly enlarged and grooved on the outer surface. Anterior mandibular teeth strongly enlarged.
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The tuber of vermis, the most posterior division of the inferior vermis, is of small size, and laterally spreads out into the large inferior semilunar lobules, which comprise at least two-thirds of the inferior surface of the hemisphere.
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Posterior parapodia have 4 compound chaetae each. The simple dorsal chaetae from chaetiger 1 is smooth, slender and unidentate. Salvatoria pilkena shows ventral simple chaetae only on most posterior chaetigers, which are sigmoid, smooth and bidentate. Its acicula is solitary and acuminate.
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Zuckerkandl's tubercle is a pyramidal extension of the thyroid gland, present at the most posterior side of each lobe. Emil Zuckerkandl described it in 1902 as the processus posterior glandulae thyreoideae.Zuckerkandl, E. (1902). Die Epithelkörperchen von Didelphys azara nebst Bemerkungen über die Epithelkörperchen des Menschen.
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The most posterior, flat, thin, and long strip of pectoral muscle is the xiphihumeralis. It is a band of parallel fibers that is found in felines but not in humans. Its origin is the xiphoid process of the sternum. The insertion is the humerus.
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Spinotrapezius, also called thoracic trapezius, is the most posterior of the three. It is triangular shaped. Posterior to the acromiotrapezius and overlaps latissimus dorsi on the front. Its origin is the neural spines of the thoracic vertebrae and its insertion is the scapular fascia.
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The fibers of the levator ani pass downward and backward to the middle line of the floor of the pelvis; the most posterior are inserted into the side of the last two segments of the coccyx; those placed more anteriorly unite with the muscle of the opposite side, in the anococcygeal body.
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Molars are the most posterior teeth in the mouth. Their function is to grind food during chewing. The number of cusps, and thus the overall appearance, vary among the different molars and between people. There are great differences between the deciduous molars and those of the permanent molars, even though their functions are similar.
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Roger Segelken Lured and liquidated, gullible male fireflies supply 'femmes fatales' with a lifesaving chemical Cornell Chronicle September 1, 1997. Retrieved November 22, 2012. In males the light organ covers the entire ventral surface of the three most posterior segments and in females it only covers a portion of the third posterior segment.Mast, S.O. 1912.
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The middle segment is the mesothorax, with the major features being the second pair of legs and the anterior wings. The third and most posterior segment, abutting the abdomen, is the metathorax, which features the third pair of legs and the posterior wings. Each segment is dilineated by an intersegmental suture. Each segment has four basic regions.
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The neck is where asexual reproduction of proglottid segments occurs. Proglottid segments are individual sets of reproductive organs that compose the rest of the cestode body. The most posterior section of the cestode body consists of multiple strobila, each being made up of several proglottids. There are 3 stages that proglottids go through in their maturation.
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The first proglottid stage is the immature stage, characterized by functional reproductive organs. The immature stage is the most anterior proglottid, and consists of anywhere between 200 and 300 proglottids. The mature proglottid is located medially to the other proglottids, and is reproductively functional and hermaphroditic. The most posterior proglottid is the gravid stage, and it is packed with eggs.
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The premedian plate is thickens as you move posterior. The posterior wall of the premedian plate concaves to form the anterior wall of the orbito-nasal cavity and shows prerostral process. The pineal plate is small, trapezoidal, thin bone that covers the most posterior part of the orbito-nasal cavity. It has a rough ornamented surface and a smooth visceral surface that has a round pineal pit.
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C. putoria undergoes three larval instar stages. After hatching from the egg, the larva in the first instar is long with 11 spine bands aligned along its 12 separate body segments. In addition, a pair of spiracles can be seen on its most posterior segment with a singular spiracular opening. During the second instar, the larva remains cream-white in color and grows to in length.
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If so, the smallest species would be P. maria and P. bellistriata, both at 7 cm (2.8 in). It had a semicircular carapace (head plate) with reniform compound eyes placed forward, which is its main characteristic. The metastoma (a large plate that is part of the abdomen) had a deep anterior triangular notch. The telson (the most posterior segment of the body) was wide and lanceolate.
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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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In females the first ray of the pelvic fin is shorter or of equal length to the second ray giving the fins a rounder appearance. There is no clear distinction between females of the three colour morphs. The dorsal fin is without a margin. The spiny portion is pale, dark and dusky orange whilst the soft parts are yellowish to clear in most posterior regions.
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PION is less common than Anterior Ischemic Optic Neuropathy (AION). Blood supply and surrounding anatomy make the anterior and posterior portions of the optic nerve susceptible to different ischemic pressures. The posterior optic nerve receives blood primarily from the pial branches of the ophthalmic artery. The optic canal, a boney tunnel leading to the brain, surrounds the most posterior part of this optic nerve segment.
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This is only partly preserved, with the cultriform process almost entirely missing. Part of its base is still attached, indicating that it would have been around 15 mm wide at the most posterior point, and not strongly set off from the basal plate of the parasphenoid. This is considered primitive in ichthyosaurs. The basal plate of the parabasisphenoid is roughly rectangular and has the processi basipterygoidei projecting from it.
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The entire row is moved posteriorly so that the anterior portion of the premaxilla contains no teeth but the most posterior portion still holds two teeth. The teeth are also situated internally to the edge of the maxilla. It was first thought that the dentary contained three parallel rows of teeth. Instead of arranging the teeth in longitudinal rows, they are now known to fall into obliquely arranged Zahnreihen.
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The right and left puborectalis unite behind the anorectal junction to form a muscular sling. Some regard them as a part of the external anal sphincter. The iliococcygeus, the most posterior part of the levator ani, is often poorly developed. The coccygeus, situated behind the levator ani and frequently tendinous as much as muscular, extends from the ischial spine to the lateral margin of the sacrum and coccyx.
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The two halves of the cartilage that make out the outer surfaces extend obliquely to cover the sides of the trachea. The posterior edge of each half articulates with the cricoid cartilage inferiorly at a joint called the cricothyroid joint. The most posterior part of the cartilage also has two projections upwards and downwards. The upper projection is called the superior horn (), and the lower is called the inferior horn.
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Mouth slightly angled downward. Lower pharyngeal plate moderately stout and broad; 2 rows of 8–9 stout molars increasing in size posteriorly and molarization flank the midline, 4 most posterior molars flattened. Spiny dorsal fin rays V." "In live, basic color olive green with tiny speckles on snout and head, particularly along the dorsal region. Speckles do not extend beyond the line between the edge of lips and the ventral edge of the orbit.
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The most posterior of the three lateral lobes is bluntly triangular. The other lateral lobes look like match heads, the anterior one larger and stretching out further from the axis. The frontal lobe is mushroom-shaped. It has schizochroal eyes with 26 vertical files (or rows), each containing five or, rarely, six lenses per file, except for a few files with less lenses at the front and back edge of the eye.
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It was ornamented with prominent scales. The telson (the most posterior segment of the body) was wide anteriorly posteriorly tapering to a lanceolate shape with a keel. It presents a marginal ornamentation of crenulated (slightly notched) margins composed of dark scales. Herefordopterus stands out for its great resemblance to Hughmilleria with derived (more "advanced") elements reminiscent of Slimonidae and Pterygotidae, such as its number of gnathobasic teeth or the ornamentation of the telson.
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This arrangement means the brain, sub-pharyngeal ganglia and the circum-pharyngeal connectives form a nerve ring around the pharynx. The ventral nerve cord (formed by nerve cells and nerve fibres) begins at the sub- pharyngeal ganglia and extends below the alimentary canal to the most posterior body segment. The ventral nerve cord has a swelling, or ganglion, in each segment, i.e. a segmental ganglion, which occurs from the fifth to the last segment of the body.
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The siphonal notch is a noticeable notch situated at the most posterior part of the aperture of the shell, through which the siphon is extended when the animal is active. The notch at the posterior end of the aperture is also called the anal notch, anal sinus, anal canal or posterior canal. Instead of a simple siphonal notch, some gastropods have an elongated siphonal canal, a hard shell tube which extends out from the anterior edge of the aperture.
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HOXD9 and HOXD10 are expressed in the developing limb throughout the entire anterior-posterior axis, followed by HOXD11, HOXD12, HOXD13, which are each expressed in more posterior regions, with HOXD13 being restricted to only the most posterior regions of the limb bud. As a result, HOXD expression clusters around the posterior ZPA (where HOXD9, 10, 11, 12, and 13 are all expressed), while less expression occurs around the AER, where only HOXD9 and HOXD10 are expressed.
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A wisdom tooth or third molar is one of the three molars per quadrant of the human dentition. It is the most posterior of the three. The age at which wisdom teeth come through (erupt) is variable, but generally occurs between late teens and early twenties. Most adults have four wisdom teeth, one in each of the four quadrants, but it is possible to have none, fewer, or more, in which case the extras are called supernumerary teeth.
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Fish of the genus Henonemus have an opercle with two odontodes (though H. triacanthopomus differs from other Henonemus in that there are three or four odontodes in specimens greater than 80 millimetres or 3.1 in SL) and the teeth of the most posterior row on the premaxilla and the dentary proximally turned to the midline then abruptly bent laterally in the distal half, and arranged in a compact band. They may grow about 4.1-9.4 centimetres (1.6-3.7 in) SL.
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The 8 upper postcanines on Abdalodon diastematicus are tricuspid, with a large minimally curved main cusp, and two smaller accessory cusps. The accessory cusps are nearly symmetrical and sit anterior and posterior to the main cusp. The roots of the postcanines are thecodont, meaning that the teeth sit in sockets in the middle of the jaw. Four upper incisors are present on both sides of the skull, with the most posterior incisor being separated from the canine by short diastema.
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All the cervicals but the most posterior and axis/atlas have hypapophyses and those triangular neural spines; all characteristics that have been described in Megalancosaurus.Specifically, the type specimen has these features, and they are corroborated in other specimens, including a complete, articulated neck with dorsal series, pectoral girdle, and forelimb. This suggests that portions of Protoavis may be drepanosaurid in nature. Chatterjee presents the skull of Protoavis as complete, although only the caudal aspect of the cranium is represented in the available fossils.
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Treatise on Invertebrate Paleontology, Part P Arthropoda 2, Chelicerata, P: 30–31. Acutiramus is classified as part of the eurypterid family Pterygotidae, a family differentiated from other eurypterids by their flattened telsons (the most posterior segment of the body) and their modified chelicerae (frontal appendages), ending in well- developed chelae (claws). Many pterygotid eurypterids, such as Jaekelopterus and Pterygotus, grew to gigantic proportions. Acutiramus was no exception, with the largest species, A. bohemicus, surpassing 2 metres (6.6 ft) in length.
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There is a type of giant pyramidal cell called Betz cells and are found just below the surface of the cerebral cortex within layer V of the primary motor cortex. The cell bodies of Betz cell neurons are the largest in the brain, approaching nearly 0.1mm in diameter. The primary motor cortex, or precentral gyrus, is one of the most important areas in the frontal lobe. The precentral gyrus is the most posterior gyrus of the frontal lobe and it lies anterior to the central sulcus.
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Restoration of E. osiliensis. Erettopterus was a big eurypterid, with E. osiliensis, the largest species, measuring approximately in length. Though this is large relative to most modern day arthropods, Erettopterus was small in comparison of many of the members of its family (the Pterygotidae), such as Jaekelopterus rhenaniae at (the largest known arthropod) and Acutiramus bohemicus at . E. grandis reached even larger sizes, , but this size is indicated by an isolated incomplete telson (the most posterior segment of the body), therefore, it is not entirely confiable.
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The specimen's remains preserve the four most posterior cervical vertebrae (likely 7-10 in regards to placement). Seven dorsal vertebrae are known, while eight dorsal ribs are known from the left side of the specimen in comparison to the five preserved for the right side. Five left uncinate processes are preserved as well. The caudal series of vertebrae are represented by 26 articulated caudal vertebrae, probably missing only the first caudal vertebra, likely making a full count of 27 caudal vertebrae in the tail.
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Their morphology resembles that of their terrestrial relative, the woodlouse; their bodies are dorsoventrally compressed, protected by a rigid, calcareous exoskeleton composed of overlapping segments. Like some woodlice, they also possess the ability to curl up into a "ball", where only the tough shell is exposed. This provides protection from predators trying to strike at the more vulnerable underside. The first shell segment is fused to the head; the most posterior segments are often fused, as well, forming a "caudal shield" over the shortened abdomen (pleon).
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Ten different air sacs attach to the lungs to form areas for respiration. The most posterior air sacs (abdominal and post-thoracic) differ in that the right abdominal air sac is relatively small, lying to the right of the mesentery, and dorsally to the liver. While the left abdominal air sac is large and lies to the left of the mesentery. The connection from the main mesobronchi to the more anterior air sacs including the interclavicular, lateral clavicular, and pre-thoracic sacs known as the ventrobronchi region.
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In his view both were part of the same map. The most posterior part of the map, in area 4, emphasized the hand and fingers and the most anterior part, in area 6, emphasized the muscles of the back and neck. Woolsey who studied the motor map in monkeys in 1956 also believed there was no distinction between primary motor and premotor cortex. He used the term M1 for the proposed single map that encompassed both the primary motor cortex and the premotor cortex.
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Scombrid fishes (tuna, mackerel and bonito) are particularly high-performance swimmers. Along the margin at the rear of their bodies is a line of small rayless, non- retractable fins, known as finlets. There has been much speculation about the function of these finlets. Research done in 2000 and 2001 by Nauen and Lauder indicated that "the finlets have a hydrodynamic effect on local flow during steady swimming" and that "the most posterior finlet is oriented to redirect flow into the developing tail vortex, which may increase thrust produced by the tail of swimming mackerel".
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Lastly, a stimulus or perceptual set switch would require a simple switch between a circle and a square. Activation is mediated by the level of abstractness of the set switch in an anterior to posterior fashion within the PFC, with the most anterior activations elicited by set switches and the most posterior activations resulting from stimulus or perceptual switches. The basal ganglia is active during response selection and the PPC, along with the inferior frontal junction are active during representation and updating of task sets called domain general switching.
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The teeth have, apart from some replacement teeth present deep in the jaw, been lost but their number, orientation and size can be inferred from the tooth sockets, which however are partly missing at the right side. These are oval and slightly elevated above the jaw bone. The first two tooth pairs were pointed somewhat to the front; the teeth more to the back pointed more sideways; the most posterior preserved stood perpendicular to the jaw. The teeth increased in size until the third pair which was the largest.
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As for most cervicals, the neural arches and spines are short, the anterior articular processes are strongly developed in that direction, and the anterior lobes of the diapophyses (bony projections to the lateral sides) extend to the bottom and lateral directions to articulate with tubercles. Seventh and eighth cervicals are the longest with long centra and posterior to them, the vertebral size slightly narrows. In most posterior cervicals, the centra are opisthocoelous with shallow posterior grooves. The dorsal vertebrae centra, unlike in the cervicals, are narrow and platycoelous with an average length of .
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Snout–vent length (SVL) is a morphometric measurement taken in herpetology from the tip of the snout to the most posterior opening of the cloacal slit (vent). It is the most common measurement taken in herpetology, being used for all amphibians, lepidosaurs, and crocodilians (for turtles, carapace length (CL) and plastral length (PL) are used instead). The SVL differs depending on whether the animal is struggling or relaxed (if alive), or various other factors if it is a preserved specimen. For fossils, an osteological correlate such as precaudal length must be used.
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When pulp testing results are inconclusive and that patients cannot localise or specify the pain or symptoms, an anaesthetic would be helpful and be used. The most posterior tooth in the area where the pain resonates undergoes anaesthesia by either infiltration or intraligamentary injection until pain diminishes. If the pain is still present, the procedure is repeated on the mesial teeth, one by one until the pain diminishes and is gone. If one can still not determine the source of the pain, the procedure will be repeated on the opposite arch.
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Descending motor pathways carry motor signals from the brain down the spinal cord and to the target muscle or organ. They typically consist of an upper motor neuron and a lower motor neuron. The lateral corticospinal tract is a descending motor pathway that begins in the cerebral cortex, decussates in the pyramids of the lower medulla (also known as the medulla oblongata or the cervicomedullary junction, which is the most posterior division of the brain) and proceeds down the contralateral side of the spinal cord. It is the largest part of the corticospinal tract.
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These findings would pave the discovery of the endogenous analgesic system. However, while most posterior researchers focused on the role of the limbic opioid system in the modulation of pain, Lico studied the role of monoamines in other regions, including the area postrema, the caudate and the medial forebrain bundle. After James Reston, while accompanying Richard Nixon in a trip to China, was subjected to post-operative acupuncture at the Anti-Imperialist Hospital in Beijing, Lico got particularly interested in how this technique could induce the activity of endogenous analgesic system. At first, Lico studied the effects of electroacupuncture on human patients.
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Erettopterus is classified as part of the eurypterid family Pterygotidae, a family differentiated from other eurypterids by their flattened telsons (the most posterior segment of the body) and their modified chelicerae (frontal appendages), ending in well-developed chelae (claws). Although some pterygotid eurypterids, such as Jaekelopterus or Acutiramus grew to gigantic proportions, it is estimated that the largest species of Erettopterus, E. osiliensis, reached . Erettopterus had a bilobed (divided into two lobes) telson, which is its main characteristic. The forms of chelicerae are very diverse between species, but they are generally very long with small curved teeth without serrations.
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Other distinguishing features include 67 to 72 lateral line scales and a total of 34 vertebrae. Swim bladder morphology is the most effective way to distinguish it between related species S. maculata and S. burrus. The swim bladder has three anterolateral extensions; not four and it differs from S. maculata in lacking well developed anterolateral extensions reaching to the level of the vent. The colour of the oriental trumpeter whiting is similar to both S. burrus and S. maculata, having blotches that are like oblique bars, but the most posterior mid-lateral dark brown blotch is elongate and reaches caudal flexure.
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Anterior () describes what is in front, and posterior () describes what is to the back of something. For example, in a dog the nose is anterior to the eyes and the tail is considered the most posterior part; in many fish the gill openings are posterior to the eyes but anterior to the tail. In projectional radiography terminology, an anteroposterior (AP) projection is taken with the X-ray generator anteriorly (such as in the front of a human), and the X-ray detector posteriorly. In contrast, a posteroanterior (PA) projection is taken with the X-ray generator posteriorly.
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Aquatic Locomotion: Electromyogram (EMG) recordings of the American eel reveal a similar pattern of muscle activation during aquatic movement as that of fish. At slow speeds only the most posterior end of the eel's muscles are activated with more anterior muscle recruited at higher speeds. As in many other animals, the muscles activate late in the lengthening phase of the muscle strain cycle, just prior to muscle shortening which is a pattern believed to maximize work output from the muscle. Terrestrial Locomotion: EMG recordings show a longer absolute duration and duty cycle of muscle activity during locomotion on land.
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A long terminal lappet is present, and is armed with two pairs of hooks. There are also two buccal suckers at the anterior extremity. The digestive organs include an anterior mouth, a pharynx larger than buccal suckers, a long wide oesophagus without diverticula and a posterior intestine that bifurcates in two lateral branches. The intestinal branches are provided with medial and lateral diverticula, joined in posterior part of opisthaptor and extending as a single branch with short diverticula to level of most posterior clamps, or not joined and one branch terminate some distance in front of the other.
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Collinearity is found between the order of the genes on the chromosome and the order in which the genes are expressed along the anteroposterior axis of the embryo. For example, the lab gene is found in the 3' position in the Antennapedia complex, and is expressed in the most anterior head region of the embryo. At the same time, the Abd-B gene is located at the 5' position of the Bithorax complex, and expressed in the most posterior region of the embryo. This suggests that the genes may be activated through a graded process, in which the action is gradually spread along the chromosome.
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Supplementary information The telson (the most posterior segment of the body), which was lanceolate and styliform, is distinctly a Eurypterus-like feature. The marginal compound eyes, the relatively large chelae and the cordate (heart-shaped) metastoma (a large plate that is part of the abdomen) show a great resemblance to Pterygotus. The carapace was parabolic or subquadrate with oval marginal eyes, the chelicerae were able to extend beyond the carapace margin and the appendages II–V were spiniferous. The genus is in various ways similar to the more derived eurypterids of its superfamily, the Pterygotioidea, however, it lacked the expanded and flattened telson that the pterygotids and Slimonia had.
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Loose valves or plates of Chiton tuberculatus from the beachdrift on Nevis, West Indies, head plates at the top, tail plates at the bottom Prepared chiton shell with structure of plates clearly visible. The most anterior plate is crescent-shaped, and is known as the cephalic plate (sometimes called a "head plate", despite the absence of a complete head). The most posterior plate is known as the anal plate (sometimes called the "tail plate", although chitons do not have tails.) The inner layer of each of the six intermediate plates is produced anteriorly as an articulating flange, called the articulamentum. This inner layer may also be produced laterally in the form of notched insertion plates.
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Consequently, this finding rejects Jones and Powell's (1970) hypothesis and thus is in conflict with Sadato et al.'s (2004) findings. A resolution to this discrepancy includes the possibility that primary sensory areas can not be classified as a single group, and thus may be far more different from what was previously thought. The multisensory syndrome with symmetric bilaterality, characterized by Gonzalo and called by this author `central syndrome of the cortex', was originated from a unilateral parieto-occipital cortical lesion equidistant from the visual, tactile, and auditory projection areas (the middle of area 19, the anterior part of area 18 and the most posterior of area 39, in Brodmann terminology) that was called `central zone'.
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Mandible of Canis variabilis from the Siberian Arctic dated at least 360,000 years old. Canis variabilis, sometimes known as the Zhoukoudian wolf, is an extinct small wolf that once inhabited part of what is now China and Yakutia. Richard H. Tedford compared C. mosbachensis (which was once distributed from Western Europe to Kazakhstan) with C. variabilis (which was once distributed from Kazakhstan to China) because they both existed in the Middle Pleistocene across mid-latitude Eurasia. The only difference he noted was that C. variabilis had "nasal bones that terminate at or anterior to the most posterior position of the frontal- maxillary suture", and therefore he proposes these two taxa to represent a variation in the one geographically widespread mid-Pleistocene wolf.
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Research done in 2000 and 2001 by Nauen and Lauder indicated that "the finlets have a hydrodynamic effect on local flow during steady swimming" and that "the most posterior finlet is oriented to redirect flow into the developing tail vortex, which may increase thrust produced by the tail of swimming mackerel". Fish use multiple fins, so it is possible that a given fin can have a hydrodynamic interaction with another fin. In particular, the fins immediately upstream of the caudal (tail) fin may be proximate fins that can directly affect the flow dynamics at the caudal fin. In 2011, researchers using volumetric imaging techniques were able to generate "the first instantaneous three-dimensional views of wake structures as they are produced by freely swimming fishes".
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Hughmilleriidae (the name deriving from the type genus Hughmilleria, which is named in honor of Scottish geologist Hugh Miller) is a family of eurypterids, an extinct group of aquatic arthropods. The hughmilleriids were the most basal members of the superfamily Pterygotioidea, in contrast with the more derived (more "advanced") families Pterygotidae and Slimonidae. Despite their classification as pterygotioids, the hughmilleriids possessed several characteristics shared with other eurypterid groups, such as the lanceolate telson (the most posterior segment of the body). Hughmilleriids are defined as pterygotioid eurypterids with swimming legs similar to those of the type genus, Hughmilleria (that is, 7th and 8th leg segments narrow and 9th segment very small), and whose second to fifth pair of appendages were spiniferous.
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Its fibers diverge; the most posterior form a thin layer, which is lost on the inferior fascia of the urogenital diaphragm; the middle fibers encircle the bulb and adjacent parts, of the corpus cavernosum urethrae, and join with the fibers of the opposite side, on the upper part of the corpus cavernosum urethrae, in a strong aponeurosis; the anterior fibers, spread out over the side of the corpus cavernosum penis, to be inserted partly into that body, anterior to the Ischiocavernosus, occasionally extending to the pubis, and partly ending in a tendinous expansion which covers the dorsal vessels of the penis. The latter fibers are best seen by dividing the muscle longitudinally, and reflecting it from the surface of the corpus cavernosum urethra.
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Support is the principle that describes how well the underlying mucosa (oral tissues, including gums) keeps the denture from moving vertically towards the arch in question during chewing, and thus being excessively depressed and moving deeper into the arch. For the mandibular arch, this function is provided primarily by the buccal shelf, a region extending laterally from the back or posterior ridges, and by the pear-shaped pad (the most posterior area of keratinized gingival formed by the scaling down of the retro-molar papilla after the extraction of the last molar tooth). Secondary support for the complete mandibular denture is provided by the alveolar ridge crest. The maxillary arch receives primary support from the horizontal hard palate and the posterior alveolar ridge crest.
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In eilenodonts, the mandibular teeth of the dentary become worn down on two sides due to contact with the maxillary and palatine teeth on the roof of the mouth. This creates two wear facets (worn away areas) in all but the most posterior teeth, converging in a 90 degree angle to form a blade-like ridge. The labial wear facet (worn-away area on the side facing the lips) was originally believed to have been positioned practically vertically while the apical (upward-facing) wear facet would have been positioned nearly horizontally, making the tooth row rectangular in cross-section. Towards the front of the jaw the wear facets shift inwards to a more diagonal position, making the tooth row triangular in cross-section.
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The pterygotids were one of the most successful eurypterid groups, with fossilised remains having been discovered on all continents except Antarctica. They are the only eurypterid group with a cosmopolitan distribution. Their remains range in age from 428 to 372 million years old (for a total temporal range of approximately 56 million years), reaching their greatest diversity during the Late Silurian, a period in time when other eurypterid groups became increasingly diverse as well. The enlargement and specialisation of the chelicerae within the Pterygotidae has been recognised as one of the two most striking evolutionary innovations within the Eurypterida, besides the transformation of the most posterior prosomal appendage into a swimming paddle (a trait seen in all eurypterids in the Eurypterina suborder).
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Among sharks, the heart consists of four chambers arranged serially (and therefore called a serial heart): blood flows into the most posterior chamber, the sinus venosus, and then to the atrium which moves it to the third chamber, the ventricle, before it reaches the conus anteriosus, which itself is connected to the ventral aorta. This is considered a primitive arrangement, and many vertebrates have condensed the atrium with the sinus venosus and the ventricle with the conus anteriosus. With the advent of lungs came a partitioning of the atrium into two parts divided by a septum. Among frogs, the oxygenated and deoxygenated blood are mixed in the ventricle before being pumped out to the body's organs; in turtles, the ventricle is almost entirely divided by a septum, but retains an opening through which some mixing of blood occurs.
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As two large pterygotids are already known from the same locality and same timespan as Necrogammarus, Erettopterus and Pterygotus, it is possible that the Necrogammarus remains, in reality, belong to one of these genera. As both genera are only diagnosed and differentiated from each other by features in body parts absent in the Necrogammarus fossil, such as the chelicerae (frontal appendages) and coxae (leg segments), it is impossible to assign Necrogammarus to either of them for the time being. Pterygotids are differentiated from other eurypterids by their flattened telsons (the most posterior segment of the body) and their modified chelicerae (frontal appendages), ending in well-developed chelae (claws). Regardless of its potential identity as either Pterygotus or Erettopterus, these features are likely to have been present in Necrogammarus as well, as all other members of the family possess them.
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Alternatively, patients missing enough teeth to compromise the predictable retention of a palatal lift prosthesis may become candidates for the fabrication of a palatal lift prosthesis with the placement of endosseous titanium implants and abutments designed to serve as retentive elements in partially edentulous and edentulous patients. Interim Palatal Lift Prostheses Retentive Clasp Assembly Retentive clasp assemblies responsible for securing interim palatal lift prostheses often benefit from the development of exaggerated retentive undercuts. Such undercuts can be bilaterally added to the most posterior dental abutments by bonding a bulk of composite resin to the buccal surface of the proposed retainers if they are adult teeth and the surfaces to which the composite resin is to be added are not restored with metallic or ceramic restorative material. When providing supplemental retentive undercuts for interim palatal lift prostheses to be retained by primary teeth or teeth whose buccal surfaces have been replaced by metallic or ceramic restorative material, the placement of orthodontic bands that harbor large buccal orthodontic brackets can serve as an alternative to the placement of composite resin.
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