|
Ornithomimus (; "bird mimic") is a genus of ornithomimid dinosaurs from the Late Cretaceous Period of what is now North America. It is usually classified into two species; the type species, ''Ornithomimus velox'', and a referred species, ''Ornithomimus edmontonicus''. ''O. velox'' was named in 1890 by Othniel Charles Marsh on the basis of a foot and partial hand from the Maastrichtian Denver Formation. Another seventeen species have been named since, though most of them have subsequently been assigned to new genera or shown to be not directly related to ''Ornithomimus velox''. The best material of species still considered part of the genus has been found in Canada, representing the earlier Edmontonian-age ''O. edmontonicus'' (named by Sternberg in 1933), known from several skeletons. ''Ornithomimus'' was a swift bipedal theropod which fossil evidence indicates was covered in feathers, equipped with a small toothless beaked head that may indicate an omnivorous diet. ==Description== Like other ornithomimids, species of ''Ornithomimus'' are characterized by feet with three weight-bearing toes, long slender arms, and long necks with birdlike, elongated, toothless, beaked skulls. They were bipedal and superficially resembled ostriches. They would have been swift runners. They had very long limbs, hollow bones, and large brains and eyes. The brains of ornithomimids in general were large for non-avialan dinosaurs, but this may not necessarily be a sign of greater intelligence; some paleontologists think that the enlarged portions of the brain were dedicated to kinesthetic coordination.〔 The bones of the hands are remarkably sloth-like in appearance, which led Henry Fairfield Osborn to suggest that they were used to hook branches during feeding. ''Ornithomimus'' differ from other ornithomimids, such as ''Struthiomimus'', in having shorter torsos, long slender forearms, very slender, straight hand and foot claws and in having hand bones (metacarpals) and fingers of similar lengths.〔Makovicky, P.J., Kobayashi, Y., and Currie, P.J. (2004). "Ornithomimosauria." In Weishampel, D.B., Dodson, P., & Osmólska, H. (eds.), ''The Dinosauria (second edition)''. University of California Press, Berkeley: 137-150.〕 The two ''Ornithomimus'' species today seen as possibly valid differ in size. In 2010 Gregory S. Paul estimated the length of ''O. edmontonicus'' at , its weight at . One of its specimens, CMN 12228, preserves a femur (thigh bone) long. ''O. velox'', the type species of ''Ornithomimus'', is based on material of a smaller animal. Whereas the holotype of ''O. edmontonicus'', CMN 8632, preserves a second metacarpal eighty-four millimetres long, the same element with ''O. velox'' measures only fifty-three millimetres. 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「Ornithomimus」の詳細全文を読む スポンサード リンク
|