Tom FORÊT

As of today, Archosaurs are represented by 2 major groups : on one side, birds are endotherm and are known for their important specific and ecological diversity. On another side, crocodilians are ectotherms and are represented by less than 30 species that all share a similar ecology. However, these groups are remnants of two much more diversified lineages with a long evolutionary history. Avemetatarsalia include pterosaurs and dinosaurs, birds included. Pseudosuchia include modern crocodilians and many other fossil organisms with very different ecologies (e.g. fully aquatic, or terrestrial). Both of these groups faced the Triassic/Jurassic mass extinction. We observe a differential response of both groups. While terrestrial Pseudosuchia are heavily affected and colonize new envrionments during the whole Jurassic, Avemetatarsalia easily cross the crisis and thrive during the whole Jurassic until achieving sometimes exceptional body sizes. My work focuses on the climatic (local temperature, CO₂ concentration,…) or biological (body size, paleophysiology,…) that may explain this differential response to the crisis. I am using the FBD (Fossilized Birth Death) model to estimate the extinction age of each Triassic/Jurassic archosaur. Then, I use phylogenetic comparative methods to test the influence of each of these variables to survival at the Triassic/Jurassic crisis.