Dissertation Research: Origin of the modern avian locomotor system across a neglected evolutionary interval: insight from new methods and new fossils

尽管鸟类飞行在生物学上是新奇的，但人们对鸟类最近的共同祖先长什么样以及他们是如何飞行的知之甚少。利用壮观的新化石材料，先进的成像技术和严格的统计方法，这项研究将重建最新的活鸟类共同祖先的最可能的解剖和功能属性，使我们更接近了解现代鸟类及其飞行能力是如何形成的。通过博物馆展览、媒体曝光和创新的在线活动，该项目具有很强的潜力，可以教育儿童和成人了解进化生物学和古生物学。研究将开始，对化石分类群的全面取样进行异速生长分析。这项分析的初步结果（基于现存鸟类的13，000个数据点）表明，现存的飞行鸟类和不会飞的鸟类之间存在基本的异速生长差异。这种分工，基于肩关节尺寸和体重之间的关系，使，第一次，划定明确的？飞行？然后呢？不会飞吗区域形态学。这种新颖的生物力学？测试？的动力飞行潜力可以很容易地应用到中生代化石，初步结果表明，收购生物力学有利的肩膀：身体质量比，使动力飞行，进化相当晚，在鸟类进化史上比传统的假设。这些结果设置了一个新的几何分析中生代干鸟postcrania，这将说明当几何现代鸟类飞行装置出现，并将揭示这种深度整合的形态系统的进化动力学阶段。接下来，该研究将集中在鸟类冠支，并将产生有史以来第一个三维原位肌肉和羽毛重建的成年现存鸟类，这将有助于强大的推断飞行肌肉形态的最新祖先现存鸟类。这将形成两个关键的化石干鸟的飞行器的运动范围模拟的基础上，从不同的现存类群的数据进行验证。总之，这里概述的项目将严格记录和机械解释脊椎动物进化史上最重要的功能转变之一？鸟类获得现代动力飞行能力。

Despite the biological novelty of avian flight, little is known about what the most recent common ancestor of birds looked like, nor about how that ancestor flew. Using spectacular new fossil material, sophisticated imaging techniques, and rigorous statistical methods, this research will reconstruct the most likely anatomical and functional attributes of the most recent common ancestor of living birds, bringing us closer to understanding how modern birds and their flying ability came to be. Through museum exhibits, media exposure, and innovative online activities, this project has strong potential to educate both children and adults about evolutionary biology and paleontology.The study will begin with allometric analysis of a comprehensive sampling of fossil taxa. Preliminary results from this analysis (based on 13,000 data points from extant birds) indicate a fundamental allometric division between extant flying and flightless birds. This division, based on the relationship between shoulder joint dimensions and body mass, enables, for the first time, the delineation of well-defined ?flying? and ?flightless? zones for morphology. This novel biomechanical ?test? of powered flying potential can easily be applied to Mesozoic fossils, and preliminary results indicate that the acquisition of a biomechanically favorable shoulder:body mass ratio, enabling powered flight, evolved considerably later in avian evolutionary history than is conventionally assumed. These results set the stage for a novel geometric analysis of Mesozoic stem bird postcrania, which will illustrate when the geometrically modern avian flight apparatus arose, and will shed light on the evolutionary dynamics of this deeply integrated morphological system. Next, the study will focus on the avian crown clade, and will generate the first ever three-dimensional in situ muscle and feather reconstructions of adult extant birds, which will facilitate the robust inference of flight muscle morphology for the most recent ancestor of extant birds. This will form the basis of range-of-motion simulations for the flight apparatus of two pivotal fossil stem birds, validated by data from diverse extant taxa. Together, the project outlined here will rigorously document and mechanically interpret one of the most important functional transitions in vertebrate evolutionary history?the acquisition of modern, powered flying ability in birds.