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''Cryolophosaurus'' ( or ; "CRY-oh-loaf-oh-SAWR-us") is a genus of large theropods known from only a single species ''Cryolophosaurus ellioti'', known from the early Jurassic period of Antarctica. It was about long and in weight, making it one of the largest theropods of its time. Individuals of this species may have grown even larger, because the only known specimen probably represents a sub-adult. ''Cryolophosaurus'' is known from a skull, a femur and other material, the skull and femur of which have caused its classification to vary greatly. The femur possesses many primitive characteristics that have classified ''Cryolophosaurus'' as a dilophosaurid or a neotheropod outside of Dilophosauridae and Averostra, where as the skull has many advanced features, leading the genus to be considered a tetanuran, an abelisaurid, a ceratosaur and even an allosaurid. Since its original description, the consensus is that ''Cryolophosaurus'' is either a primitive member of the Tetanurae or a close relative of that group. ''Cryolophosaurus'' possessed a distinctive crest on its head that spanned the head from side to side, similar to a Spanish comb. Based on evidence from related species and studies of bone texture, it is thought that this bizarre crest was used for intra-species recognition. The brain of ''Cryolophosaurus'' was also more primitive than those of other theropods. ''Cryolophosaurus'' was first excavated from Antarctica's Early Jurassic, Sinemurian to Pliensbachian aged Hanson Formation, formerly the upper Falla Formation, by paleontologist Dr. William Hammer in 1991. It was the first carnivorous dinosaur to be discovered in Antarctica and the first non-avian dinosaur from the continent to be officially named. The sediments in which its fossils were found have been dated at ~194 to 188 million years ago, representing the Early Jurassic Period. ==Description== The holotype FMNH PR1821 is the only fully described specimen of ''Cryolophosaurus''. The specimen consists of an incomplete skull and mandibles lacking most of their front half; nine maxillary teeth; a fragmentary sixth cervical centrum; cervical vertebrae 7-10; several posterior cervical ribs; several anterior dorsal vertebrae; most mid and posterior dorsal vertebrae; several dorsal ribs; the fifth sacral vertebrae; three chevrons; many partial and complete caudal vertebrae and centra; two partial humeri; a proximal radius; a proximal ulna; a partial ilium; a proximal pubis; both ischia, but only one distal; two incomplete femora; the distal end of a tibia; the distal end of a fibula, and the astragalus and calcaneum.〔 In 2013, new material of ''Cryolophosaurus'' was unearthed in Antarctica. The description of this material has not yet been published in a non-abstract form. ''Cryolophosaurus'' was a large, well-built theropod, one of the largest of its time. The genus has been described by Roger Benson and colleagues (2012) as a top predator in Antarctica. It had slender proportions.〔 ''Cryolophosaurus'' was estimated as being in length by William R. Hammer & William J. Hickerson (1998).〔 A 2007 study by Nathan Smith ''et al.'' revised the length to .〔 Its weight estimated at .〔〔 Based on these length and weight estimates, ''Cryolophosaurus'' is currently the largest known Early Jurassic theropod.〔〔 Smith ''et al.'' (2007b) and Benson ''et al.'' (2012) noted that the holotype individual probably represents a sub-adult, so adults could have been larger.〔〔 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「Cryolophosaurus」の詳細全文を読む スポンサード リンク
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