Evolution of key biological characteristics in dinosaurs and their relatives

恐龙及其近亲，包括翼龙和鳄鱼，组成了爬行动物类群--始祖龙。在中生代的大部分时间里，始祖龙主导着大型陆生脊椎动物的生态位，而被称为鸟类的改良恐龙约占1万个现存物种。始祖龙的生物学特征肯定有助于解释它们的成功，但始祖龙生物学的许多方面只能在活着的鸟类和鳄鱼身上直接研究。对于已灭绝的始祖龙，必须使用化石证据、与现存动物的比较以及生物力学建模等方法来推断它们。 我的实验室将研究始祖龙及其近亲的关键功能能力的进化，特别是通风和陆地运动。通风是空气进入和排出身体的过程，这对始祖龙来说很有趣，因为鸟类和鳄鱼都有单向的肺(即只允许空气单向流动的肺)。此外，这两类动物的肋骨都有被称为钩突的凸缘，用于固定呼吸肌肉，但鳄鱼鲜为人知的钩突在解剖学上与鸟类的不同。需要对各种已灭绝的始祖龙的呼吸系统进行研究，以确定鸟类和鳄鱼在这一领域的相似性是反映了共同的原始始祖龙特征，还是仅仅是趋同的进化。 同样，灭绝的始祖龙的陆地运动也带来了许多重要的问题。在始祖龙的早期历史上，从伸展的蜥蜴状的后肢姿势转变为直立的姿势，但这种转变的细节尚不确定，在同一进化阶段，前肢姿势的进化几乎没有被探索过。恐龙的陆地运动得到了更好的研究，但一些主要的问题仍然没有得到解决，包括为什么鸟腿类恐龙和一些兽脚类动物的耻骨干会独立地“倒转”(即向后旋转)。 我的实验室将通过将肌肉骨骼数字建模技术应用于选定的化石标本来解决始祖龙通风和陆地运动的主要问题。后肢和前肢的模型将被用来量化参数，如肌肉瞬间手臂，这使得测试关于姿势和运动的假设成为可能。躯干骨骼的模型将揭示各种始祖龙的呼吸运动，以及钩突和其他附属结构的作用。将这些功能研究的结果放在始祖龙系统发育的背景下，将有助于推断始祖龙内部运动和通风的进化，有助于识别可能对始祖龙生态成功做出贡献的功能创新。

Dinosaurs and their close relatives, including pterosaurs and crocodilians, comprise the reptilian group Archosauria. Archosaurs dominated large terrestrial vertebrate niches throughout most of the Mesozoic, and the modified dinosaurs known as birds account for about 10,000 living species. The biological characteristics of archosaurs must help to explain their success, but many aspects of archosaurian biology can be studied directly only in living birds and crocodilians. For extinct archosaurs, they must be inferred using fossil evidence, comparisons to living animals, and approaches such as biomechanical modelling. My lab will investigate the evolution of key functional capabilities, particularly ventilation and terrestrial locomotion, in archosaurs and their close relatives. Ventilation, the process of moving air into and out of the body, is intriguing in archosaurs because both birds and crocodilians have a unidirectional lung (i.e. one allowing airflow in only one direction). Furthermore, the ribs of both groups bear flanges called uncinate processes that anchor ventilatory muscles, but the poorly known uncinate processes of crocodilians differ anatomically from those of birds. Studies of the ventilatory system in various extinct archosaurs are needed to determine whether the similarities in this domain between birds and crocodilians reflect shared, primitive archosaurian features or merely convergent evolution. Similarly, terrestrial locomotion in extinct archosaurs presents many important problems. A shift from a sprawling, lizard-like hindlimb posture to an upright one occurred in the early history of Archosauria, but the details of this transition are uncertain, and the evolution of forelimb posture during the same evolutionary interval is nearly unexplored. Terrestrial locomotion in dinosaurs is better studied, but some major questions remain unresolved, including why the shaft of the pubis became independently “retroverted” (i.e. rotated posteriorly) in ornithischian dinosaurs and some theropods. My lab will address major issues of archosaur ventilation and terrestrial locomotion by applying musculoskeletal digital modelling techniques to selected fossil specimens. Models of the hindlimbs and forelimbs will be used to quantify parameters such as muscle moment arms, making it possible to test hypotheses about posture and locomotion. Models of the trunk skeleton will shed light on ventilatory movements in various archosaurs, and the role of uncinate processes and other accessory structures. Placing the results of these functional studies in the context of archosaur phylogeny will permit inferences about the evolution of locomotion and ventilation within Archosauria, facilitating identification of functional innovations that may have contributed to archosaurian ecological success.