意外北票龙(兽脚类:镰刀龙类)头部骨骼学研究（英文）

Cranial osteology of Beipiaosaurus inexpectus(Theropoda: Therizinosauria)

意外北票龙(Beipiaosaurus inexpectus)是研究镰刀龙类演化的关键物种,自从徐星等1999年简短报道以来就未被详细描述。对意外北票龙正型标本头部骨骼进行了详细研究。意外北票龙的头部骨骼结构有些独特之处,如额骨的眶后骨突大且明显外侧延伸、顶骨有一细长的前突、顶骨的鳞骨突腹侧支加长以及外下颌孔背腹侧深且位置非常靠后。一系列头部骨骼的祖征(如较大的齿骨和齿骨联合缝处下弯角度较小)揭示意外北票龙是镰刀龙类的一个早期演化分支,符合先行研究所提出的结论。新的数据不只对了解意外北票龙的头部骨骼结构非常重要,更对镰刀龙类演化的研究有显著意义。

Beipiaosaurus inexpectus, a key taxon for understanding the early evolution of therizinosaurians, has not been fully described since it was briefly reported on by Xu, Tang and Wang in 1999. Here we present a detailed description of the cranial anatomy of the holotype of this theropod dinosaur. B. inexpectus is unique in some of its cranial features such as the postorbital process of the frontal is large and its abrupt transition from the orbital rim, a long and sharp anterior process of the parietal, the elongate ventral ramus of the squamosal process of parietal, and external mandibular fenestra deep dorsoventrally and extremely posteriorly located. A number of plesiomorphic cranial features(such as relatively large dentary and less downturned degree of dentary symphysis) suggest that B. inexpectus is an early-branching Therizinosaurian, as proposed by previous studies. New information derived from our study is not only important for our understanding of the cranial anatomy of B. inexpectus but also significant to the study of the evolution of Therizinosauria.