张氏西峡爪龙(兽脚类：阿尔瓦雷斯龙类)第二跖骨的骨组织学及其对“窄足型”足部结构发育的启示（英文）

Metatarsal Ⅱ osteohistology of Xixianykus zhangi(Theropoda: Alvarezsauria) and its implications for the development of the arctometatarsalian pes

阿尔瓦雷斯龙类的一晚期演化支——张氏西峡爪龙(Xixianykus zhangi),是体型最小的非鸟兽脚类恐龙之一。与其他阿尔瓦雷斯龙类类似,其胫跗骨和足部相对较长,并具有善于奔跑的兽脚类恐龙中常见的窄足型足部,指示其可能非常善于奔跑。对张氏西峡爪龙的第二跖骨进行了骨组织学研究,发现了两种罕见的骨组织学结构:放射状骨脉管和沙比纤维。认为这两种结构与其具有的窄足型足部有关,然而还需要对更多的兽脚类跖骨进行骨组织学研究来验证这一结论。

The late-branching alvarezsaurian Xixianykus zhangi is among the smallest known non-avialan theropods. With great similarity to its close relatives, it is highly cursorial as indicated by proportionally long lower segments of the hindlimbs and the presence of an arctometatarsalian pes-a highly modified structure that has been suggested to improve cursorial capability in theropods. Here we describe the osteohistology of the metatarsal Ⅱ of the holotype of X. zhangi(XMDFEC V 0011). Two rarely reported histological features, radial vascular canals and Sharpey’s fibers, are presented in this study. We suggest that both features are related to the development of the arctometatarsalian pes;however, further investigations of metatarsal osteohistology in theropods are required for the validation of our interpretation.