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''Akidolestes cifellii'' is an extinct mammal which dates to the early Cretaceous period, 124.6 million years ago. It is part of the Yixian Formation in Liaoning, China. The description is based on a nearly complete skeleton, partially complete skull, and an impression. It is notable in that it displays characteristics of monotremes but appears to be more related to modern therian mammals. ''Akidolestes'' has no modern relatives. It is an early offshoot of mammal related to therians (the subclass containing marsupials and placentals). It clearly belongs within a group of theriiform mammals known as the Spalacotherioidea. Unlike other members of this superfamily, however, ''Akidolestes'' has some very prototherian features. Cervical ribs are present, a condition previously known only from monotremes and basal mammals such as ''Repenomamus'' and ''Fruitafossor''. ''Akidolestes'' is also monotreme-like in the shape of its pubis, and in aspects of hindlimb posture. Overall, however, other aspects of the appendicular skeleton, dental characters, and cranial characters strongly suggest that ''Akidolestes'' falls well within the Spalacotherioidea and does represent an early branch of theriiform mammal. Luo and Li suggest that these primitive characters were reacquired in this group as a result of either convergence or through a modification of a developmental pathway to a prior state. The genus name, ''Akidolestes'', is derived from ''akido'', Greek for point, and ''lestes'', Greek for thief. Akido- refers to the pointed snout and -lestes is a common suffix for fossil mammals. The specific epithet, ''cifelli'', is in honor of Richard L. Cifelli, a prominent researcher in prehistoric mammals. ==References== * Li, G. and Z.-X. Luo. 2006. "A Cretaceous symmetrodont therian with some monotreme-like postcranial features". ''Nature'', 439:195–200. 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「Akidolestes」の詳細全文を読む スポンサード リンク
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