Macroevolutionary trends within Metriorhynchidae (Crocodylia): an integrated quantitative approach

Metriorhynchid crocodylians represent the pinnacle of marine specialisation within Archosauria; not only were they a major component of the Middle Jurassic to Early Cretaceous marine ecosystems, but provide further examples that extinct crocodylians did not all resemble their modern extant relatives. Here a varied toolkit of techniques, including cladistics, geometric morphometrics, discrete character disparity analysis and biomechanical finite element analysis, is used to examine the macroevolutionary history of this clade. All analyses demonstrate that metriorhynchids became more divergent in terms of biodiversity, form and function up until the Jurassic-Cretaceous boundary, after which there is no evidence for recovery or further radiations. A clear evolutionary trend towards hypercarnivory in Dakosaurus is supported by phylogenetic character optimisation, morphometrics and FEA, which also support specialised piscivory within Rhacheosaurus and Cricosaurus. Within Metriorhynchidae there is a consistent trend towards increasing marine specialisation, with the hypermarine Cricosaurus exhibiting numerous convergences with other Mesozoic marine reptiles.