封面说明：意外北票龙(Beipiaosaurus inexpectus) 复原图。意外北票龙是早期分化出的一种镰刀龙类兽脚类恐龙，是镰刀龙类早期进化研究中的关键物种，但自徐星等1999 年的简短报道以来，还未有过详细的形态描述。其头骨包含一系列祖征，如较大的齿骨和齿骨联合缝处下弯角度较小，以及部分衍征，如额骨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。详见廖俊棋和徐星文(p. 117)。 ( 绘图：陈瑜)

Cover image: Artist rendering of Beipiaosaurus inexpectus. B. inexpectus is an early-branching therizinosaurian theropod. Despite being a key taxon for understanding the early evolution of therizinosaurians, it has never been fully described since the brief report published by Xu et al. in 1999. The skull of the holotype of B. inexpectus exhibits a number of plesiomorphic features, such as relatively large dentary and less downturned degree of dentary symphysis, and some apomorphic features, including 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 suggest that B. inexpectus is an early-branching Therizinosauria, as proposed by previous studies. See details in the paper of Liao and Xu (p. 117). (Illustrated by Chen Yu)