Evolution of key biological characteristics in dinosaurs and their relatives

恐龙和它们的近亲，包括翼龙和鳄鱼，组成了爬行动物类群初龙。在中生代的大部分时间里，祖龙统治着大型陆生脊椎动物的生态位，而被称为鸟类的变异恐龙占了大约10,000个现存物种。主龙类的生物学特征必须有助于解释它们的成功，但主龙类生物学的许多方面只能在活的鸟类和鳄鱼身上直接研究。对于灭绝的祖龙，必须使用化石证据，与活动物的比较以及生物力学建模等方法进行推断。 我的实验室将研究主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，空气进出身体的过程，在主龙中很有趣，因为鸟类和鳄鱼都有一个单向的肺（即只允许一个方向的气流）。此外，这两个群体的肋骨都带有称为钩突的凸缘，钩突可以锚住肌肉，但鳄鱼的钩突在解剖学上与鸟类的钩突不同。需要对各种已灭绝的主龙类的进化系统进行研究，以确定鸟类和鳄鱼类在这一领域的相似性是否反映了共同的原始主龙类特征，或者仅仅是趋同进化。 同样地，已经灭绝的主龙类在陆地上的运动也提出了许多重要的问题。从一个蔓延，蜥蜴般的后肢姿势到直立的姿势的转变发生在初龙类的早期历史中，但这种转变的细节是不确定的，在同一进化间隔期间前肢姿势的进化几乎是未知的。恐龙在陆地上的运动已经得到了更好的研究，但是一些主要的问题仍然没有解决，包括为什么鸟臀目恐龙和一些兽脚亚目恐龙的耻骨轴独立地“后倾”（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祖龙通风和陆地运动的主要问题。后肢和前肢的模型将用于量化肌肉力矩臂等参数，从而可以测试有关姿势和运动的假设。躯干骨骼的模型将阐明各种主龙类的排泄运动，以及钩突和其他附属结构的作用。将这些功能的研究结果的背景下，初龙类的运动和通风的进化将允许推论，促进识别功能的创新，可能有助于初龙类的生态成功。

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.