A NEW ENANTIORNITHINE BIRD FROM THE LOWER CRETACEOUS OF WESTERN LIAONING, CHINA, AND ITS IMPLICATIONS FOR EARLY AVIAN EVOLUTION
A NEW ENANTIORNITHINE BIRD FROM THE LOWER CRETACEOUS OF WESTERN LIAONING, CHINA, AND ITS IMPLICATIONS FOR EARLY AVIAN EVOLUTION
复制标题
DOI：
10.1080/02724634.2012.652321
复制
发表时间：
2012-01-01
影响因子：
1.4
通讯作者：
Sullivan, Corwin
中科院分区：
文献类型：
--
作者：
Hu, Dongyu;Xu, Xing;Sullivan, Corwin
最近的研究已经模糊了两个主要鸟类类群的区别：反鸟目，白垩纪早期鸟类的主要辐射，和鸟形目，包括现存鸟类的分支。本文描述了辽宁西部早白垩世九佛堂组一种新的反鸟鸣鸟Xiangornis shenmi，gen.et sp.nov.这进一步减小了两组之间的形态学差距。Xiangornis shenmi有几个对映鸟氨酸的功能，包括一个叉与显着延长hypocleidium，喙突与凸的外侧边缘，和一个小掌骨，比大掌骨进一步向远端延伸。然而，它也具有一些衍生的鸟类特征，例如短掌骨（约为大掌骨的六分之一长），完全融合到大掌骨，掌骨上的大伸肌突，小掌骨和大掌骨之间的近端和远端融合，以及掌骨间空间位于掌骨远端。这一新发现表明，与现代鸟类相似的腕掌形态可能在反鸟兽中独立进化，并且出现得比鸟形目更早，并表明早期鸟类的性格进化比以前认为的更复杂。
Recent studies have blurred the distinctness of two major avian groups: the Enantiornithes, a major radiation of early birds in the Cretaceous, and the Ornithuromorpha, the clade including extant birds. Here we describe a new enantiornithine bird from the Lower Cretaceous Jiufotang Formation of western Liaoning, China, Xiangornis shenmi, gen. et sp. nov., which further reduces the morphological gap between the two groups. Xiangornis shenmi has several enantiornithine features, including a furcula with a significantly elongated hypocleidium, a coracoid with a convex lateral margin, and a minor metacarpal that extends further distally than the major metacarpal. However, it also possesses some derived ornithurine features, such as a short alular metacarpal (about one-sixth as long as the major metacarpal) that is completely fused to the major metacarpal, a large extensor process on the alular metacarpal, proximal and distal fusion between the minor and major metacarpals, and an intermetacarpal space positioned significantly distal to the alular metacarpal. This new find indicates that a carpometacarpal morphology similar to that seen in modern birds probably evolved independently in enantiornithines and appeared earlier than in Ornithuromorpha, and demonstrates that character evolution in early birds was more complex than previously believed.