Meeting Abstract
Paleoneurology bolsters our understanding of brain evolution through deep time. Archosauria, represented today by birds and crocodylians, has long been of interest to paleoneurologists. Croc-line archosaurs, despite low modern diversity, have potential for investigating brain evolution due to their numerous ecological transitions, extensive fossil record, and robust systematics. To analyze braincase endocast variation and probe for a connection between neuromorphology and ecology, we combined high-density 3D geometric morphometric data from crocodylian braincase endocasts with phylogenetic comparative methods to identify regime shifts in an OU framework. Our dataset contains 22 endocasts of 16 extant and six extinct species. Landmarks were sampled from four brain regions: cerebrum, optic lobe, cerebellum, and medulla. Each brain region was found to form a distinct module and were analyzed separately. Regime configuration hypotheses, including ecologically-based snout shape and habitat preference, were identified and tested for the whole brain and each brain region. For the cerebrum, optic lobe, and cerebellum, the best fitting regime hypotheses recovered a shift at crown-group Crocodylia or Neosuchia. For the whole brain and medulla, a shift was found in the crown, between crocodyloids and alligatoroids. This suggests the medulla is driving overall brain shape. Finally, ecological regime hypotheses varied in their fit for brain regions, suggesting regions vary in their response to ecology. Future work is needed to elucidate primary drivers of shifts within the crocodylian brain.
