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''Hadrocodium wui'' (''hadro'' from Greek ἁδρός/''hadros'', "large, heavy, fullness"; Latin: ''codium'', from Greek κώδεια/''kodeia'', "head (a plant )" (alluding to its enlarged cranial cavity);〔https://www.ncbi.nlm.nih.gov/pubmed/11375489〕 and ''wui'', the Latinized version of discoverer Xiao-Chun Wu's name〔) is an extinct mammaliaform that lived during the Sinemurian stage of the Early Jurassic approximately in the Lufeng basin in what is now the Yunnan province in south-western China (, paleocoordinates ).〔. Retrieved April 2013.〕 The fossil of this mouse-like, paper-clip sized animal was discovered in 1985 but was then interpreted as a juvenile morganucodontid.〔 ''Hadrocodium'' remained undescribed until 2001; since then its large brain and advanced ear structure have greatly influenced the interpretation of the earliest stages of mammalian evolution, as these mammalian characters could previously be traced only to some . ''Hadrocodium'' is known only from a skull, but the body is estimated to have been a mere in length and about in mass, making it one of the smallest mammals ever. ''Hadrocodium'' may have been the first animal to have a nearly fully mammalian middle ear. It is the earliest known example of several features possessed only by mammals,〔(Symmetrodonta - Palaeos )〕 including the middle-ear structure characteristic of modern mammals and a relatively large brain cavity.〔 These features had been considered limited to the crown group mammals, who emerged in the Middle Jurassic; the discovery of ''Hadrocodium'' suggests that these attributes appeared earlier (45 million years earlier) than previously thought. Whether ''Hadrocodium'' was warm-blooded or cold-blooded has not been settled, although its apparent nocturnal features would seem to place it in the endotherm group. ==Family Tree== (詳細はProbainognathia |2= }} }} }} }} }} }} }} }} 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「Hadrocodium」の詳細全文を読む スポンサード リンク
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