The role of cranial biomechanics and feeding in clade diversification and early dinosaur evolution

新的解剖适应和进食机制通常被认为是引发主要进化支多样化的“关键创新”。然而，这些适应的机制很少得到定量或严格的测试，严重破坏了这些假设的有效性。此外，大多数生物力学分析都是在单个范例生物上进行的，而比较系统发育背景对于理解摄食对进化史的影响和测试宏观进化假设至关重要。恐龙在陆地生态系统中统治了大约1.3亿年，展示了巨大的身体大小、形状和生态。最早的恐龙和它们的祖先是多面手和次要的动物组成部分。在晚三叠纪-早侏罗世（2.3 - 1.8亿年前），恐龙的体型、多样性和丰度急剧增加，各种因素都与恐龙的成功有关。人们认为，新的进食适应性的出现允许了生态多样化。然而，这种引人入胜的“功能故事”并没有在定量的、假设驱动的比较框架中得到检验，而且以前的工作主要集中在具有极端形态的衍生恐龙分类群（例如，暴龙、梁龙）上，而忽略了接近恐龙基础的形式。由于这些原因，恐龙是一个理想的模型系统，可以将摄食生物力学数据与系统发育相结合，从而更严格地研究功能多样性与进化动态之间的关系。在这个项目中，我们的目标是全面了解恐龙起源和早期进化过程中恐龙头骨生物力学功能变化的后果，这是生命史上的关键时刻。考虑到生物力学分析的尖端计算方法的可用性和整合以及早期恐龙及其祖先的新发现，拟议的项目尤其及时。我们将整合古生物学、生物学和工程学的原理和方法，重建15个早期恐龙和恐龙类群的头骨解剖和功能。CT扫描和可视化软件将用于创建三维计算机模型。来自原始化石和现存鳄鱼、鸟类和蜥蜴的信息将用于重建头部肌肉组织。利用这些重建和多体动力学分析，我们将模拟颌骨在喂养过程中的运动，估计沿牙齿排的咬合力并计算最大颌闭合速度。我们将把动态模型的结果与有限元分析和几何形态计量学相结合，以测试颅骨对喂食引起的载荷的反应。此外，我们将对三种现存物种进行模拟，以确保模型预测的准确性。这些分析的结果将为早期恐龙的颚功能和潜在饮食提供证据，以及它们是否在进化过程中变得更加专业化。最后，我们将把进食特征的出现与恐龙多样性模式进行比较，以确定进食在它们的早期进化和成功中所起的作用。古生物学家，解剖学家，生物力学家，进化生物学家和工程师将从这项工作中受益，这将为在活体和化石动物中执行进化生物力学设定新的基准，并将建立新的英国，欧洲和海外合作。该项目还将产生新的方法进步，可以应用于其他分支和其他功能问题。最后，这项工作的技术和视觉方面及其对早期恐龙的关注将吸引公众，提供大量的参与机会和媒体的兴趣，这将有助于提高公众对科学原理和方法的理解，并将确保这项工作的广泛传播。

Novel anatomical adaptations and mechanisms for feeding are often postulated as 'key innovations' that spark the diversification of major clades. However, the mechanics of these adaptations are rarely quantitatively or rigorously tested, seriously undermining the validity of these hypotheses. Moreover, the majority of biomechanical analyses are carried out on single exemplar organisms, whereas a comparative phylogenetic context is critical to understanding the impact of feeding on evolutionary history and testing macroevolutionary hypotheses. Dinosaurs dominated terrestrial ecosystems for >130 million years, exhibiting a tremendous range of body sizes, shapes and ecologies. The earliest dinosaurs and their ancestors were generalists and minor faunal components. Dramatic increases in body size, diversity and abundance occurred during the Late Triassic-Early Jurassic (230-180 million years ago), and various factors have been implicated in dinosaur success. It is thought that the appearance of novel feeding adaptations permitted ecological diversification. However, this engaging 'functional story' has not been tested in a quantitative, hypothesis-driven comparative framework and previous work has focused on derived dinosaur taxa with extreme morphologies (e.g., Tyrannosaurus, Diplodocus), ignoring forms close to the base of Dinosauria. For these reasons, dinosaurs are an ideal model system for integrating data on feeding biomechanics with phylogeny, allowing more rigorous investigation of the relationship between functional diversity and clade dynamics. In this project we aim to comprehensively understand the consequences of functional changes in dinosaur skull biomechanics during the origin and early evolution of dinosaurs, a key moment in life's history. The proposed project is particularly timely given the availability and integration of cutting-edge computational methods for biomechanical analyses and new discoveries of early dinosaurs and their ancestors.We will integrate principles and methods from palaeontology, biology and engineering to reconstruct skull anatomy and function in 15 early dinosaur and dinosauriform taxa. CT scans and visualization software will be used to create 3D computer models. Information from the original fossils and living crocodilians, birds and lizards will be used to reconstruct head musculature. Using these reconstructions and multi-body dynamics analysis, we will model jaw motions during feeding, estimate bite forces along the tooth row and calculate maximum jaw closing speed. We will integrate results from dynamic models with finite element analysis and geometric morphometrics to test how the skulls respond to feeding-induced loads. In addition, we will run simulations on three living species to ensure model predictions are accurate. Results from these analyses will provide evidence for the jaw function and potential diet of early dinosaurs, and whether they became more specialized in terms of feeding performance during their evolution. Finally, we will compare the appearance of feeding characters to dinosaur diversity patterns to determine what role feeding had in their early evolution and success. Palaeontologists, anatomists, biomechanists, evolutionary biologists and engineers will benefit from this work, which will set new benchmarks for performing evolutionary biomechanics in living and fossil animals and will establish new UK, European and overseas collaborations. This project will also generate new methodological advances that can be applied to other clades and other functional questions. Finally, the technological and visual aspects of this work and its focus on early dinosaurs will appeal to the general public, offering numerous engagement opportunities and media interest that will contribute to increased public understanding of scientific principles and methods, and will ensure wide dissemination of this work.