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Ornithothoraces is a group of avialans that includes all enantiornithines ("opposite birds") and the euornithes ("true birds"), which contains modern birds and their ancestors. The name Ornithothoraces means "bird thoraxes". This refers to the modern, highly advanced anatomy of the thorax that gave the ornithothoracines superior flight capability compared to more primitive avialans. This anatomy includes a large, keeled breastbone, elongated coracoids and a modified glenoid joint in the shoulder, and a semi-rigid rib cage. The earliest known members of the group are the enantiornithes ''Protopteryx fengningensis'' and ''Eopengornis martini'', as well as the euornithine ''Archaeornithura meemannae'', all from the Sichakou Member of the Huajiying Formation in China, which has been dated to 130.7 million years old. At least one other enantiornithine, ''Noguerornis gonzalezi'', may be even older, at up to 145.5 million years ago, though its exact age is uncertain.〔Holtz, Thomas R. Jr. (2012) ''Dinosaurs: The Most Complete, Up-to-Date Encyclopedia for Dinosaur Lovers of All Ages,'' (Winter 2011 Appendix. )〕 ==Classification== In 1994, Chiappe and Calvo established a phylogenetic definition of the group. They defend Ornithothoraces as a node-based clade, the common ancestor of ''Iberomesornis romerali'' and modern birds, and all of its other descendants.〔Chiappe, Luis; Calvo, J.O. (1994) "''Nequenornis volans'', a new Late Cretaceous bird (Enantiornithes:Avisauridae) from Patagonia, Argentina". ''Journal of Vertebrate Paleontology'' 14:230-246.〕 In 1998, Paul Sereno defined Ornithothoraces in the same way, but used ''Sinornis santensis'' instead of ''Iberomesornis romerali''.〔Sereno, Paul (1998). "A rationale for phylogenetic definitions, with application to the higher-level taxonomy of Dinosauria". ''Neues Jahrbuch fur Geologie und Palaontologie'' 210:41-83.〕 The cladogram below follows the results of a phylogenetic analysis by Lee ''et al.'', 2014: }} }} }} }} }} }} }} }} }} }} }} }} }} }} }} 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「ornithothoraces」の詳細全文を読む スポンサード リンク
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