From baby birds to feathered dinosaurs incipient wings and the evolution of flight

Reconstructing the tree of life requires deciphering major evolutionary transformations and the functional capacities of fossils with “transitional” morphologies. Some of the most iconic, well-studied fossils with transitional features are theropod dinosaurs, whose skeletons and feathered forelimbs record the origin and evolution of bird flight. However, in spite of over a century of discussion, the functions of forelimb feathers during the evolution of flight remain enigmatic. Both aerodynamic and non-aerodynamic roles have been proposed, but few of the form-function relationships assumed by these scenarios have been tested. Here, we use the developing wings of a typical extant ground bird (Chukar Partridge) as possible analogues/homologues of historical wing forms to provide the first empirical evaluation of aerodynamic potential in flapping theropod “protowings.” Immature ground birds with underdeveloped, rudimentary wings generate useful aerodynamic forces for a variety of locomotor...重建生命之树需要厘清重大演化转变，以及具有‘过渡性’形态的化石的功能特性。其中辨识度最高、研究最充分的过渡特征化石类群当属兽脚类恐龙（theropod dinosaurs），它们的骨骼结构与带羽前肢完整记录了鸟类飞行的起源与演化历程。然而，尽管相关讨论已延续百余年，前肢羽毛在飞行演化过程中的功能仍未明晰。学界已提出空气动力学与非空气动力学两类功能假说，但上述假说所依托的形态-功能关联鲜少得到实证检验。本研究以典型现生地栖鸟类——石鸡（Chukar Partridge）的发育中翼作为史前翼形态的潜在类比/同源结构，首次对扑动的兽脚类‘原翼（protowings）’的空气动力学潜力开展实证评估。翼发育尚未完全、结构简陋的幼年地栖鸟类可产生可供多种运动模式利用的有效空气动力……