Meeting Abstract
Crocodylians have long been viewed as the modern expression of a stable evolutionary core that has maintained a conservative ecomorphology since the Jurassic. From this core, more specialized groups with distinct environmental preferences (semiterrestrial, marine) or feeding styles (piscivorous, durophagous) arose independently. New discoveries reveal unexpected complexity in neosuchian phylogeny. Although groups outwardly resembling modern crocodiles and alligators (e.g., goniopholidids) and gharials (e.g., pholidosaurids) were present throughout the Jurassic and Cretaceous, the closest relatives of Crocodylia were generally small (approximately 2 m) durophagous animals with short, robust snouts and bulbous posterior teeth. They resembled early alligatorids, which suggests that character states currently diagnosing Alligatoroidea and subordinate clades may be plesiomorphic at more inclusive levels; this, in turn, might help resolve the ongoing debate over the phylogenetic relationships of modern gharials as a rooting problem. The outwardly generalized ecomorphology of modern crocodylians represents multiple specializations from a differently specialized common ancestor. Features previously used to characterize crocodylians, such as a secondary palate and vertebral procoely, had more complex histories with multiple gains and losses; indeed, they may precede the origins of Crocodyliformes. Groups unlike modern species, including semiterrestrial predators and small durophagous forms, arose within Crocodylia multiple times throughout the Cenozoic and even into the Neogene, falsifying the popular image of crocodylians as evolutionary static living fossils.
