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Therizinosaurs (or segnosaurs) were theropod dinosaurs belonging to the clade Therizinosauria. Therizinosaur fossils have been found in Early through Late Cretaceous deposits in Mongolia, the People's Republic of China and Western North America. Various features of the forelimbs, skull and pelvis unite them quite comfortably, both as theropods and, as maniraptorans, close relatives to birds. The name ''therizinosaur'' is derived from the Greek θήριζω, ''therizo'' meaning 'to reap' or 'to cut off' and ''sauros'' meaning 'lizard'. The older name ''segnosaur'' is derived from Latin ''segnis'' meaning 'slow' or 'sluggish' and Greek σαυρος, ''sauros'' meaning 'lizard'. ==Description== Therizinosaurs had a very distinctive, often confusing set of characteristics. Their long necks, wide torsos, and hind feet with four toes used in walking resembled those of basal sauropodomorph dinosaurs. Their unique hip bones, which pointed backwards and were partially fused together, initially reminded paleontologists of the "bird-hipped" ornithischians. Among the most striking characteristics of therizinosaurs are the enormous claws on their hands, which reached lengths of around one meter in ''Therizinosaurus''. The unusual range of motion in therizinosaur forelimbs, which allowed them to reach forward to a degree other theropods could not achieve, also supports the idea that they were mainly herbivorous. Therizinosaurs may have used their long reach and strongly curved claws to grasp and shear leafy branches, in a manner similar to the ground sloths.〔 * Burch, S. (2006). "The range of motion of the glenohumeral joint of the therizinosaur ''Neimongosaurus yangi'' (Dinosauria: Theropoda)." ''Chicago Biological Investigator'', 3(2): 20. (Abstract).〕 Skin impressions from ''Beipiaosaurus'' indicate that therizinosaurs were covered with a coat of primitive, down-like feathers similar to those seen in the compsognathid ''Sinosauropteryx'', as well as longer, simpler, quill-like feathers that may have been used in display.〔〔Xu X., Zheng X.-t. and You, H.-l. (2009). "A new feather type in a nonavian theropod and the early evolution of feathers." ''Proceedings of the National Academy of Sciences (Philadelphia)'', . 〕 Therizinosaurs spanned a large range of sizes, from the small ''Beipiaosaurus'' (which measured 2.2 m, or 7.3 ft in length),〔Xu, X., Tang, Z-L., and Wang, X-L. (1999). "A therizinosauroid dinosaur with integumentary structures from China." ''Nature'', 399(6734): 350-354.〕 to the gigantic ''Therizinosaurus'', which at an approximate 10 m (33 ft) long and an estimated weight of 5 tonnes,〔Paul, G.S., 2010, ''The Princeton Field Guide to Dinosaurs'', Princeton University Press p. 160〕 was among the largest known theropods. 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「Therizinosaur」の詳細全文を読む スポンサード リンク
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