摘  要：反鸟类在白垩纪鸟类进化上出现了多样的进化分支，然而发生在这些进化分支上生态作用的形态学特化认识一直以来并不深刻。本文报道发现在中国东北地区热河生物群保存精美的早白垩世鸟类标本，指（趾）爪的形态学表明反鸟类发生过较为独特的生态特化，新的标本在形态学上具有韩氏周鸟正型标本无法形态学比较识别的特征，尽管后者有点大。

新的韩氏周鸟标本在头骨上提供了前所未知的重要信息，将进一步对所知的一些反鸟类颅骨解剖和演化的特征进行全面补充，同时也增进了我们对于韩氏周鸟头后骨骼最近公认的演化特征的认识，这件标本成为认识韩氏周鸟最为完整的反鸟类标本之一，必将会促进下一步的深入研究。

New information on the anatomy of the Chinese Early Cretaceous Bohaiornithidae (Aves: Enantiornithes) from a subadult specimen of Zhouornis hani

Zhang Yuguang et al.

Abstract：Enantiornithines are the most diverse avian clade in the Cretaceous. However, morphological specializations indicative of specific ecological roles are not well known for this clade. Here we report on an exquisitely well-preserved specimen from the Lower Cretaceous Jehol Group of northeastern China, which pedal morphology is suggestive of a unique ecological specialization within Enantiornithes. The morphology of the new specimen is largely indistinguishable from that of the holotype of the bohaiornithid enantiornithine Zhouornis hani, albeit the latter is somewhat larger.The new specimen provides important and previously unknown details of the skull of Zhouornis hani, which add to the limited knowledge about the cranial anatomy and evolution of  enantiornithines. The information offered by the new specimen also augments our understanding of the postcranial morphology of bohaiornithid enantiornithines, a clade that has been only recently recognized.With the description of this specimen, Zhouornis hani becomes one of the most anatomically complete known enantiornithine species, which will facilitate future  morphological studies.

From Zhang Yuguang et al. 2014, PeerJ 2:e407; DOI 10.7717/peerj.1-19