Pei Rui, Pittman Michael, Goloboff Pablo A, Dececchi T Alexander, Habib Michael B, Kaye Thomas G, Larsson Hans C E, Norell Mark A, Brusatte Stephen L, Xu Xing
Key Laboratory of Vertebrate Evolution and Human Origins, Institute of Vertebrate Paleontology & Paleoanthropology, Chinese Academy of Sciences, Beijing 100044, China.
Vertebrate Palaeontology Laboratory, Division of Earth and Planetary Science, The University of Hong Kong, Pokfulam, Hong Kong SAR, China.
Curr Biol. 2020 Oct 19;30(20):4033-4046.e8. doi: 10.1016/j.cub.2020.06.105. Epub 2020 Aug 6.
Uncertainties in the phylogeny of birds (Avialae) and their closest relatives have impeded deeper understanding of early theropod flight. To help address this, we produced an updated evolutionary hypothesis through an automated analysis of the Theropod Working Group (TWiG) coelurosaurian phylogenetic data matrix. Our larger, more resolved, and better-evaluated TWiG-based hypothesis supports the grouping of dromaeosaurids + troodontids (Deinonychosauria) as the sister taxon to birds (Paraves) and the recovery of Anchiornithinae as the earliest diverging birds. Although the phylogeny will continue developing, our current results provide a pertinent opportunity to evaluate what we know about early theropod flight. With our results and available data for vaned feathered pennaraptorans, we estimate the potential for powered flight among early birds and their closest relatives. We did this by using an ancestral state reconstruction analysis calculating maximum and minimum estimates of two proxies of powered flight potential-wing loading and specific lift. These results confirm powered flight potential in early birds but its rarity among the ancestors of the closest avialan relatives (select unenlagiine and microraptorine dromaeosaurids). For the first time, we find a broad range of these ancestors neared the wing loading and specific lift thresholds indicative of powered flight potential. This suggests there was greater experimentation with wing-assisted locomotion before theropod flight evolved than previously appreciated. This study adds invaluable support for multiple origins of powered flight potential in theropods (≥3 times), which we now know was from ancestors already nearing associated thresholds, and provides a framework for its further study. VIDEO ABSTRACT.
鸟类（鸟纲）及其近亲系统发育的不确定性阻碍了对早期兽脚亚目恐龙飞行的更深入理解。为了帮助解决这一问题，我们通过对兽脚亚目工作组（TWiG）虚骨龙类系统发育数据矩阵进行自动分析，得出了一个更新的进化假说。我们基于TWiG得出的更大、分辨率更高且评估更好的假说支持将驰龙科 + 伤齿龙科（恐爪龙下目）归为鸟类（近鸟类）的姐妹分类单元，并恢复了晓廷龙亚科作为最早分化的鸟类。尽管系统发育将继续发展，但我们目前的结果提供了一个恰当的机会来评估我们对早期兽脚亚目恐龙飞行的了解。利用我们的结果以及有羽小翼羽龙类的现有数据，我们估计了早期鸟类及其近亲进行动力飞行的潜力。我们通过祖先状态重建分析来实现这一点，计算动力飞行潜力的两个指标——翼载荷和比升力的最大和最小估计值。这些结果证实了早期鸟类具有动力飞行潜力，但在最接近鸟纲的近亲（某些伶盗龙亚科和小盗龙亚科驰龙科）的祖先中这种情况很罕见。我们首次发现这些祖先中有很大一部分接近表明具有动力飞行潜力的翼载荷和比升力阈值。这表明在兽脚亚目恐龙飞行进化之前，对翼辅助运动的尝试比之前认为的要多。这项研究为兽脚亚目恐龙动力飞行潜力的多次起源（≥3次）提供了宝贵的支持，我们现在知道这起源于已经接近相关阈值的祖先，并为其进一步研究提供了一个框架。视频摘要。
