Meeting Abstract
Today, the 27 modern crocodylian species display similar morphologies and occupy comparable ecological niches in their semi-aquatic environments. However, Crocodylomorpha, the group that includes includes the extinct relatives of living crocodylians, has an evolutionary history of more than 200 million years, which is reflected by a rich fossil record. Extinct crocodylomorphs exhibited much higher morphological disparity than extant ones, as well as remarkable ecological diversity, ranging from fully marine to completely terrestrial forms. In particular, cranial shape in crocodylomorphs seems to be integrated with ecological factors (such as feeding strategies), given the biomechanical implications of skull elongation and shortening. Nevertheless, the influence of ecological transitions on crocodylomorph cranial shape was never comprehensively investigated. I used geometric morphometric techniques and phylogenetic comparative methods to analyze cranial shape variation and disparity in crocodylomorphs and fully characterize its macroevolutionary patterns. I found a significant influence of ecological lifestyles (i.e. terrestrial, aquatic, and semi-aquatic) on cranial shape, as well as a strong size-shape relationship, indicating allometric shape changes (mainly in the snout region). Furthermore, I found that terrestrial species are more disparate in terms of cranial shape, particularly the mainly small-bodied notosuchians. I also found that aquatic and semi-aquatic forms are usually associated with regime shifts to more longirostrine crania and to larger body sizes. This suggests an intricate relationship between cranial shape, body size and ecology, and that clade-specific adaptations to different environmental conditions are determining large scale patterns of crocodylomorph cranial shape evolution.
