Characterising macroevolutionary patterns within crocodylomorpha

Crocodylians today comprise only 24 recognised species, and are often regarded as morphologically conservative. However, the fossil record of crocodylomorphs, which includes the extinct relatives of crocodylians, is much richer and extends over the last ~220 million years. This great biodiversity is reflected in their morphological disparity, with crocodylomorph species occupying a much wider range of ecological niches. Research effort has concentrated mostly on the description of new taxa and on placing them within the crocodylomorph evolutionary tree, and has greatly contributed to our understanding of crocodylomorph phylogeny and diversity. Nevertheless, another fundamental aspect of crocodylomorph macroevolution, morphological disparity, has only recently been the subject of quantitative scrutiny, with the focus often limited to specific subgroups rather than the entire clade. In this thesis, crocodylomorph morphological disparity is quantitatively assessed using distinct types of data. Body size patterns, characterised via a model-fitting approach, provide new insights into the adaptive landscape of crocodylomorphs. Patterns of cranial shape variation suggest an important link between ecological diversification and morphological disparity. Finally, the action of heterochrony, underlying remarkable cranial modifications in the crocodylomorph clade Notosuchia, is tested using geometric morphometrics. Together, these results represent a significant contribution to better understanding crocodylomorph phenotypic evolution