关键词: 鸟类, 飞行起源, 树栖说, 地栖说, 关键结构

Abstract: The origin of bird flight is a disputed issue in the field of evolutionary biology over past decades．The initial study mostly focused on the discussion of the evolutionary path（e．g．，the cursorial versus arboreal hypothesis）for bird flight，and more recently，more studies have been made concerning the transitions of key flight structure such as skeletons and muscles in the process of the origin of the flight of birds．This paper aims to provide a brief introduction of the history of the study of bird flight and present a summary of some recent studies in this area give a summary introduction in the recent progress and existing debate from the two aspects mentioned above．

Key words: Birds，Origin of flight，Cursorial hypothesis，Arboreal hypothesis，Key structure