ABSTRACT

The holotype and only known specimen of Adalatherium hui from the Late Cretaceous of Madagascar preserves the first postcranial skeleton for the Gondwanatheria. It represents only the fourth Mesozoic mammaliaform described from articulated postcranial material from Gondwana (the others being the morganucodontans Megazostrodon and Erythrotherium and the stem therian Vincelestes). The postcranial skeleton of Adalatherium is virtually complete, and its preservation is exceptional; even costal cartilages and manual and pedal sesamoids are preserved. Adalatherium exhibits a variety of derived and plesiomorphic traits, probably reflective of a long evolutionary history in geographic isolation on Madagascar. Among the bizarre features are a mediolaterally compressed and anteroposteriorly bowed tibia, an unusually high number of trunk vertebrae (at least 16 thoracic and 12 lumbar vertebrae), a short tail, and a trochleated navicular facet on the astragalus. Aside from these features, Adalatherium displays derived and plesiomorphic characteristics in its pectoral girdle: the coracoid is well developed and contributes to half of the glenoid fossa, a separate procoracoid is absent, and the sternoclavicular joint appears to have been mobile. A ventrally facing scapular glenoid and the well-developed humeral trochlea suggest a relatively parasagittal forelimb posture. Notable features of the hind limb and pelvic girdle include a large obturator foramen similar in size to that of therians, a large parafibula, and the presence of epipubic bones. Articulation between the pelvic girdle and hind limb is in contrast to that between the pectoral girdle and the forelimb in that it is indicative of a sprawling posture.

摘要

来自马达加斯加晚白垩世的唯一全称的Adalatherium hui标本保留了冈瓦纳特里亚的第一个颅后骨架。它仅代表从冈瓦纳的关节后颅骨材料中描述的第四种中生哺乳动物形式（其他是摩根巨齿兽Megazostrodon和Erythrotherium以及茎therian Vincelestes）。Adalatherium的颅后骨架实际上是完整的，并且保存极为出色。甚至保留了肋软骨，手动和踏板的芝麻。Adalatherium表现出多种衍生和多形性状，可能反映了马达加斯加地理上孤立的悠久进化史。其中一个怪异的特征是胫骨的中外侧压缩和前后弯曲的胫骨，数量异常多的躯干椎骨（至少16个胸椎和12个腰椎椎骨），短尾巴以及在黄芪上有一个旋转的小舟小平面。除了这些功能之外，Adalatherium在其胸带中显示出派生性和多形性特征：喙突发育良好，占盂盂的一半，不存在单独的喙突，胸锁关节似乎活动。面对肩骨的肩len盂和发达的肱骨滑车表明前矢状位相对较近。后肢和骨盆带的显着特征包括一个大的闭孔，其大小类似于蒂安人，大的腓骨，以及耻骨。骨盆带和后肢之间的关节运动与胸带和前肢之间的关节运动相反，因为它表明了肢体伸展的姿势。