Bernard Price Institute for Palaeontological Research, University of the Witwatersrand, , Johannesburg 2050, South Africa.
Proc Biol Sci. 2010 Mar 7;277(1682):787-94. doi: 10.1098/rspb.2009.1440. Epub 2009 Nov 11.
Aardonyx celestae gen. et sp. nov. is described from the upper Elliot Formation (Early Jurassic) of South Africa. It can be diagnosed by autapomorphies of the skull, particularly the jaws, cervical column, forearm and pes. It is found to be the sister group of a clade of obligatory quadrupedal sauropodomorphs (Melanorosaurus + Sauropoda) and thus lies at the heart of the basal sauropodomorph-sauropod transition. The narrow jaws of A. celestae retain a pointed symphysis but appear to have lacked fleshy cheeks. Broad, U-shaped jaws were previously thought to have evolved prior to the loss of gape-restricting cheeks. However, the narrow jaws of A. celestae retain a pointed symphysis but appear to have lacked fleshy cheeks, demonstrating unappreciated homoplasy in the evolution of the sauropod bulk-browsing apparatus. The limbs of A. celestae indicate that it retained a habitual bipedal gait although incipient characters associated with the pronation of the manus and the adoption of a quadrupedal gait are evident through geometric morphometric analysis (using thin-plate splines) of the ulna and femur. Cursorial ability appears to have been reduced and the weight bearing axis of the pes shifted to a medial, entaxonic position, falsifying the hypothesis that entaxony evolved in sauropods only after an obligate quadrupedal gait had been adopted.
Aardonyx celestae gen. et sp. nov. 是从南非上埃利奥特组（早侏罗世）描述的。它可以通过头骨的独特特征来诊断，特别是颚骨、颈椎、前肢和后肢。它被发现是一个强制性四足蜥脚形亚目恐龙（Melanorosaurus + Sauropoda）的姐妹群，因此位于基础蜥脚形亚目-蜥脚类恐龙过渡的核心。A. celestae 的狭窄下颚保留了一个尖的联合处，但似乎缺乏肉质的脸颊。宽阔的 U 形下颚以前被认为是在失去限制张口的脸颊之前进化而来的。然而，A. celestae 的狭窄下颚保留了一个尖的联合处，但似乎缺乏肉质的脸颊，这表明在蜥脚类动物的大下巴进食器官的进化中存在未被认识的趋同现象。A. celestae 的四肢表明它保留了习惯性的两足步态，尽管与手的旋前和四足步态的采用相关的初期特征通过对尺骨和股骨进行几何形态测量分析（使用薄板样条）是明显的。奔跑能力似乎已经降低，后足的承重轴转移到内侧的轴下位置，这推翻了只有在采用强制性四足步态之后，轴下位置才在蜥脚类动物中进化的假说。
