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''Ceratosaurus'' meaning "horned lizard", in reference to the horn on its nose (Greek ''κερας/κερατος, keras/keratos'' meaning "horn" and ''σαυρος''/''sauros'' meaning "lizard"), was a large predatory theropod dinosaur from the Late Jurassic Period (Kimmeridgian to Tithonian), found in the Morrison Formation of North America, and the Lourinhã Formation of Portugal (and possibly the Tendaguru Formation in Tanzania). It was characterized by large jaws with blade-like teeth, a large, blade-like horn on the snout and a pair of hornlets over the eyes. The forelimbs were powerfully built but very short. The bones of the sacrum were fused (synsacrum) and the pelvic bones were fused together and to this structure〔Sereno 1997〕 (i.e. similar to modern birds). A row of small osteoderms was present down the middle of the back. ==Description== ''Ceratosaurus'', at first glance, looked like a fairly typical theropod, however its skull was quite large in proportion to the rest of its body, and large nasal and brow horns and possessed a prominent nose horn formed from protuberances of the nasal bones. In addition to the large nasal horn, ''Ceratosaurus'' possessed smaller hornlike ridges in front of each eye, similar to those of ''Allosaurus'', these ridges were formed by enlargement of the lacrimal bones. Uniquely among theropods, ''Ceratosaurus'' possessed dermal armor, in the form of small osteoderms running down the middle of its back. Its tail comprised about half of the body's total length and was thin and flexible with high vertebral spines.〔 The type specimen was an individual about long; it is not clear whether this animal was fully grown.〔 David B. Norman (1985) estimated that the maximum length of ''Ceratosaurus'' was , an assessment supported by a particularly large ''Ceratosaurus'' specimen from the Cleveland-Lloyd Quarry (UMNH 5728), discovered in the mid-1960s, which may have been long assuming similar proportions to the holotype. Marsh (1884) suggested that ''Ceratosaurus'' weighed about half as much as ''Allosaurus''.〔 In ''Predatory Dinosaurs of the World'', published in 1988, Gregory S. Paul estimated that the ''C. nasicornis'' holotype skeleton came from an animal weighing about while the large material from the Cleveland-Lloyd Quarry represents a much bigger and heavier individual, whose bulk he estimated at about . The bigger specimen was later assigned by James H. Madsen and Samuel P. Welles to the new species ''C. dentisulcatus''. A considerably lower figure was proposed by John Foster, a specialist on the Morrison Formation, in 2007. Foster used an equation provided by J.F. Anderson and colleagues to estimate mass from femur length, which yielded an approximate weight of for ''C. magnicornis'' and for ''C. dentisulcatus''.〔 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「Ceratosaurus」の詳細全文を読む スポンサード リンク
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