Evolution of key biological characteristics in dinosaurs and their relatives

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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.