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''Baryonyx'' () is a genus of theropod dinosaur which lived in the Barremian stage of the early Cretaceous Period, about 130–125 million years ago. The holotype specimen was discovered in 1983 in Surrey, England, and the animal was named ''Baryonyx walkeri'' in 1986. The genus name, ''Baryonyx'', means "heavy claw" and alludes to the animal's very large claw on the first finger; the specific name (''walkeri'') refers to its discoverer, amateur fossil hunter William J. Walker. Fragmentary specimens were later discovered in other parts of the United Kingdom and Iberia. The holotype specimen is one of the most complete theropod skeletons from the UK, and its discovery attracted media attention. ''Baryonyx'' was about long and weighed , but the holotype specimen may not have been fully grown. It had a long, low snout and narrow jaws, which have been compared to those of a gharial. The tip of the snout expanded to the sides in the shape of a rosette. Behind this, the upper jaw had a notch which fit into the lower jaw (which curved upwards in the same area). It had a triangular crest on the top of its nasal bones. ''Baryonyx'' had many finely serrated, conical teeth, with the largest teeth in front. The neck was less curved than that of other theropods, and the neural spines of its dorsal vertebrae increased in height from front to back. It had robust forelimbs, with the eponymous first-finger claw measuring about long. Now recognised as a member of the family Spinosauridae, ''Baryonyx'' affinities were obscure when it was discovered. Apart from the type species (''B. walkeri''), some researchers have suggested that ''Suchomimus tenerensis'' belongs in the same genus and that ''Suchosaurus cultridens'' is a senior synonym; however, subsequent authors have kept them separate. ''Baryonyx'' was the first theropod dinosaur demonstrated to have been piscivorous (fish-eating), as evidenced by fish scales in the stomach region of the holotype specimen. It may also have been an active predator of larger prey and a scavenger, since it also contained bones of a juvenile ''Iguanodon''. The creature would have caught and processed its prey primarily with its forelimbs and large claws. ''Baryonyx'' lived near water bodies, in areas where other theropod, ornithopod, and sauropod dinosaurs have also been found. ==Description== In 2010, ''Baryonyx'' was estimated to have been long and to have weighed . It was estimated at in 1997 and and in 1988. The fact that elements of the skull and vertebral column of the ''B. walkeri'' holotype specimen (NHM R9951) do not appear to have co-ossified (fused) suggests that the individual was not fully grown, and the mature animal may have been much larger (as attested by the size of the related ''Spinosaurus'', which reached about and . However, the specimen's fused sternum indicates that it may have been fairly mature.〔 The second-best-preserved specimen (ML1190) was about the same size as the holotype skeleton.〔〔 The skull of ''Baryonyx'' is incompletely known, and much of the middle and hind portions are not preserved. It was elongated, and the front 170 mm (6.6 in) of the premaxillae formed a long, low snout (rostrum) with a rounded upper surface. The nostrils, far back from the tip, passed horizontally from one side of the skull to the other. The front 130 mm (5.1 in) of the snout expanded into a spatulate (flared outwards to the sides), "terminal rosette" shape similar to the modern gharial, and the front 70 mm (2.7 in) of the lower margin was downturned. The snout was very narrow just behind the rosette. The creature's maxilla and premaxilla fit together in a complex articulation, resulting in a strongly-curved tooth row. The gap in the row is comparable to that of ''Dilophosaurus''. The front 140 mm (5.5 in) of the dentary in the mandible curved upwards towards this area, and the gap between the upper and lower jaw is known as the subrostral notch. The snout had extensive pits (which would have been exits for blood vessels and nerves), and the maxilla appears to have housed sinuses.〔 ''Baryonyx'' had a rudimentary secondary palate, similar to crocodiles but unlike most theropod dinosaurs.〔 A rugose surface suggests the presence of a horny pad in the roof of the mouth. The upper midline of the nasal bones had a triangular sagittal crest, which was narrow and sharp in front. The lacrimal bone appears to have formed a horn core similar to those seen, for example, on ''Allosaurus''. The dentary was very long and shallow, with a prominent Meckelian groove. The rest of the lower jaw was fragile; the hind third was much thinner than the front, with a blade-like appearance. The front part of the dentary curved outwards to accommodate the large front teeth, and this area formed the mandibular part of the rosette. The dentary had many foramina (openings), which were passages for nerves and blood vessels.〔 It has been suggested that some of ''Baryonyx'' cranial bones had been misidentified (resulting in the occiput's too-deep reconstruction), and the skull was probably as low, long and narrow as that of the closely-related genus ''Suchomimus''.〔 Most of the teeth found with the holotype specimen were not attached to the skull; a few remained in the upper jaw, and only small replacement teeth were in the lower jaw. The teeth had the shape of recurved cones, flattened somewhat sideways. Although the larger teeth were less recurved than the smaller ones, they were otherwise uniform. The roots were very long, and the teeth slender. The carinae (edges) of the teeth were finely serrated with denticles on the front and back. There were seven narrow, uniform denticles per millimetre (0.039 in), more than in most theropods. The creature's teeth were fluted, with six to eight ridges along the length of their inner sides and fine-grained enamel. The inner side of each tooth row had a bony wall. The number of teeth was large, with seven teeth in the right premaxilla (other theropods have three to five) and thirty-two in the dentary, where sixteen is typical. The lower jaw would have had sixty-four teeth, and the difference between the number of teeth in the upper and lower jaws is more pronounced than in other theropods. The teeth in the dentary were more densely-packed than those in the maxilla, and probably smaller. The terminal rosette in the upper jaw had thirteen dental alveoli (tooth sockets), six on the left and seven on the right side; the first four were large (with the second and third the largest), while the fourth and fifth progressively decreased in size. The diameter of the largest was twice that of the smallest. The first four alveoli of the dentary (corresponding to the tip of the upper jaw) were the largest, with the rest more regular in size. Interdental plates were between the alveoli.〔 The neck formed a straighter ''S'' shape (a sigmoid curve typical of theropods) than that seen in other theropods; in fact, the neck was initially thought to lack the ''S'' curve. The shape of the cervical vertebrae indicate that they tapered towards the head and were progressively longer front to back. The neural spines of the cervical vertebrae were low, thin, and were not always sutured to the centra (the bodies of the vertebrae). The axis vertebra, small relative to the size of the skull, had a well-developed hyposphene. The centra of the dorsal vertebrae were similar in size. Like other dinosaurs, ''Baryonyx'' reduced its weight (skeletal pneumaticity) with fenestrae (openings) in the neural arches and with pleurocoels (hollow depressions) in the centra (primarily near the transverse processes). From front to back, the neural spines of the dorsal vertebrae changed from short and stout to tall and broad.〔 The scapulae (shoulder blades) were robust; the bones of the forelimb were short in relation to the animal's size, but broad and sturdy. The humerus was short and stout, with its ends broadly expanded and flattened—the upper side for the deltopectoral crest and muscle attachment and the lower for articulation with the radius and ulna. The radius was short, stout and straight, and the olecranon of the ulna apparently very powerful. The lower part of the ulna had a broad expansion. The first finger had a large claw (ungual bone) measuring about along its curve, which would have been lengthened by a keratin sheath in life. Apart from its size, the claw's proportions were fairly typical of a theropod; it was bilaterally symmetric, slightly compressed, smoothly rounded, and sharply pointed. A groove for the sheath ran along the length of the claw. The pubic foot of the pelvis was not expanded.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Baryonyx」の詳細全文を読む スポンサード リンク
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