Evolution of Body Form, Posture, and Locomotion in Birds and Dinosaurs

鸟类从非鸟类恐龙的进化是脊椎动物古生物学的一个长期兴趣，在过去的几十年里，由于方法的进步和令人兴奋的新化石的发现，这一问题得到了严格的研究。身体形态、姿势和运动的创新代表了这一转变过程中关键的生态形态变化。然而，虽然特别强调了前肢的修改和飞行的起源，但专注于后肢进化的研究却很少，而且主要是定性的。运动是一个全身的任务，后肢可以提供丰富的信息，以测试有关鸟类进化的假设，并评估飞行起源的生态环境。事实上，就总体解剖学变化而言，鸟类在使用蜷缩的后肢姿势方面是独一无二的（不像它们更直立的祖先），理论上可以预测这种特征会降低运动效率，从而导致性能损失。该项目旨在解决这些问题，并构建一个更全面的观点，鸟类运动进化，通过调查的假设下，蹲后肢姿势进化的选择，以增强运动性能的分支机构，其中变形下的动物的重量。为了实现这一点，实验数据将收集从活禽行走和跳跃的表面上不同的顺应性。这些数据将为蹲伏姿势的生物力学提供新的见解，并可以与解剖信息相结合，以验证鸟类运动的计算机模型。这些模型将用于通知化石类群的模拟，允许量化肢体姿势的进化变化对性能的影响。通过跟踪形态和功能的进化，后肢的作用可以更好地整合到更广泛的鸟类进化的生态形态学理论。这将使我们能够理解，例如，如果有效地利用蹲下的两足动物在动力飞行的进化之前，因此作为一个exaptation通过干鸟类可以有效地在树栖环境中飞行，许多理论已经提出了鸟类飞行进化背后的选择压力。然而，迄今为止，还没有人提供化石描述的大体解剖和体型变化与支撑这一重大生态转变的生物力学之间的机械联系。在这里，我们提出了一个新的假设：身体形状和姿势的变化最初是由选择增强跳跃和行走性能的兼容基板（即分支）。收集鸟类在受控实验室环境中在不同顺应性的坚硬基底和树枝上跳跃和行走的生物力学数据。利用3D摄影测量和压力传感器收集动物园中鸟类在不同顺应性的坚硬基底和树枝上跳跃和行走的生物力学数据。利用OBJ1的数据验证鸟类跳跃和行走的计算机模型.使用经过验证的计算机模拟方法来模拟鸟线化石中观察到的总体解剖变化的影响，以量化对在坚硬与柔顺基底上行走和跳跃的生物力学性能的影响。该项目基于鸟类树栖性和飞行进化的新生态形态学假设。这是一个有争议和深入研究的领域，我们希望将新的实验和计算机模拟应用于我们的新假设将产生重大影响。如果得到支持，我们的假设将是第一个在早期鸟类进化过程中提供总体解剖变化，生物力学和主要生态变化（即飞行起源）之间的整体联系。

The evolution of birds from non-avian dinosaurs is a long-standing interest in vertebrate palaeontology, which has been rigorously investigated over the past few decades, driven by methodological advances and the discovery of exciting new fossils. Innovations in body form, posture, and locomotion represent key ecomorphological changes across this transition. However, while particular emphasis has been placed on modifications to the forelimb and the origins of flight, studies focusing on hind limb evolution have been scarcer and primarily qualitative in nature. Locomotion is a whole-body task, and the hind limb may provide a wealth of information with which to test hypotheses about avian evolution, and assess the ecological context of the origins of flight. Indeed, in terms of gross anatomical changes, birds are unique in their use of a crouched hindlimb posture (unlike their more erect dinosaurian ancestors), a trait which might theoretically be predicted to incur performance penalties, by decreasing the efficiency of locomotion. This project seeks to address these issues and construct a more holistic view of avian locomotory evolution, through investigation of the hypothesis that crouched hind limb posture evolved under selection for enhanced locomotor performance on branches, which deform under the animal's weight. To achieve this, experimental data will be collected from live birds walking and jumping on surfaces of varying compliance. This data will provide new insights into the biomechanics of crouched posture, and can be combined with anatomical information to validate computer models of avian locomotion. These models will be used to inform simulations of fossil taxa, allowing quantification of the performance impact of evolutionary changes to limb posture. By tracking the evolution of morphology and function, the role of the hind limb can be better integrated into broader ecomorphological theories of avian evolution. This will allow us to understand, for example, if the efficient use of crouched bipedalism preceded the evolution of powered flight, and therefore served as an exaptation through which stem birds could locomote effectively in an arboreal setting.Numerous theories have been proposed as selective pressures behind the evolution of flight in birds. However, to-date none have provided a mechanistic link between changes in gross anatomy and body shape described by fossils and the biomechanics underpinning this major ecological shift. Here we propose a new hypothesis: that changes in body shape and posture were initially driven by selection for enhanced jumping and walking performance on compliant substrates (i.e. branches).To investigate the correlation between gross anatomical changes and arboreal locomotor modes in birds by:1. Collecting biomechanical data on birds jumping and walking on hard substrates and branches of varying compliance in a controlled laboratory setting.2. Collecting biomechanical data on birds jumping and walking on hard substrates and branches of varying compliance in zoos using 3D videophotogrammetry and pressure sensors.3. Using data from OBJ1 to validate a computer model of birds jumping and walking.4. Use the validated computer simulation approach to model the impact of gross anatomical changes seen in bird-line fossils to quantify effects on biomechanical performance on walking and jumping on hard vs. compliant substrates.This project is grounded in a new ecomorphological hypothesis for the evolution of arboreality and flight in birds. This is a contentious and intensely researched area and we expect that application of novel experiments and computer simulations to our new hypothesis will make a major impact. If supported, our hypothesis will be the first provide a holistic link between gross anatomical changes, biomechanics and major ecological shifts (i.e. the origin of flight) during early bird evolution.