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''Protoceratops'' (; from Greek ''proto-/πρωτο-'' "first", ''cerat-/κερατ-'' "horn" and ''-ops/-ωψ'' "face", meaning "First Horned Face") is a genus of sheep-sized (1.8 m long) herbivorous ceratopsian dinosaur, from the Upper Cretaceous Period (Campanian stage) of what is now Mongolia. It was a member of the Protoceratopsidae, a group of early horned dinosaurs. Unlike later ceratopsians, however, it was a much smaller creature that lacked well-developed horns and retained some primitive traits not seen in later genera. ''Protoceratops'' had a large neck frill which was likely used as a display site to impress other members of the species. Other hypotheses about its function include protection of the neck and anchoring of jaw muscles, but the fragility of the frill and the poor leverage offered by possible attachment sites here makes these ideas implausible. Described by Walter W. Granger and W.K. Gregory in 1923, ''Protoceratops'' was initially believed to be an ancestor of the North American ceratopsians. Researchers currently distinguish two species of ''Protoceratops'' (''P. andrewsi'' and ''P. hellenikorhinus''), based in part by their respective sizes. In the 1920s, Roy Chapman Andrews discovered fossilized eggs in Mongolia that were interpreted as belonging to this dinosaur, but which turned out to be those of ''Oviraptor''. ==Description== ''Protoceratops'' was a quadrupedal dinosaur that was partially characterized by its distinctive neck frill at the back of its skull. The frill itself contained two large parietal fenestra (holes in the frill), while its cheeks had large jugal bones. The exact size and shape of the neck frill varied by individual; some specimens had short, compact frills, while others had frills nearly half the length of the skull. The frill consists mostly of the parietal bone and partially of the squamosal. Some researchers, including Peter Dodson〔 attribute the different sizes and shapes of these bones to sexual dimorphism, as well as the age of the specimen, at the time of death. ''Protoceratops'' was approximately 1.8 meters (6 ft) in length and 0.6 meters (2 ft) high at the shoulder. A fully grown adult would have weighed less than 400 pounds (180 kg).〔"Protoceratops." In: Dodson, Peter & Britt, Brooks & Carpenter, Kenneth & Forster, Catherine A. & Gillette, David D. & Norell, Mark A. & Olshevsky, George & Parrish, J. Michael & Weishampel, David B. ''The Age of Dinosaurs''. Publications International, LTD. p. 118-119. ISBN 0-7853-0443-6.〕 Smaller specimen are estimated at .〔Seebacher, F. 2001. ''A new method to calculate allometric length-mass relationships of dinosaurs.'' Journal of Vertebrate Paleontology 21 (1). p. 53〕 The large numbers of specimens found in high concentration suggest that ''Protoceratops'' lived in herds.〔 ''Protoceratops'' was a relatively small dinosaur with a proportionately large skull. ''Protoceratops'' appears to have had muscular jaws capable of a powerful bite. These jaws were packed with dozens of teeth, well suited for chewing tough vegetation.〔 The skull consisted of a massive frontal beak, and four pairs of fenestrae (skull openings). The foremost hole, the naris, was considerably smaller than the nostrils seen in later genera. ''Protoceratops'' had large orbits (the holes for its eyes), which measured around 50 millimeters in diameter.〔 Behind the eye was a slightly smaller fenestra, known as the "infratemporal fenestra." 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「Protoceratops」の詳細全文を読む スポンサード リンク
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