Crocodylia (Including Gharials Crocodiles and Alligators)

Abstract

The order Crocodylia contains the sole reptilian survivors of the Archosauria, which also includes the dinosaurs and birds. While the living forms are not nearly as diverse as they have been in the past, they represent a lineage that first appeared in the Mesozoic Era, and that has successfully survived a number of extinction events. They also represent a group that has been seriously impacted by humans, both in terms of hunting and habitat destruction. Crocodylyians are, therefore, largely protected or endangered. However, they are critical apex predators that often serve as ‘keystone’ species and indicators of the health of the environments that they inhabit. Key Concepts The Crocodylia (the only living non‐avian Archosaurs) are aquatic or semi-aquatic apex predators that can trace their origins to the early Mesozoic Era. The three recognized families, Alligatoridae, Crocodylidae and Gavialidae, are currently represented by some 30 named forms found primarily in tropical or subtropical environments. The combination of human hunting for their meat and skins, habitat loss and long generation times have contributed to the threatened or endangered status of many living crocodylians. Even though most recognized species seem to be valid hybridization, especially within the genus Crocodylus, is common and complicates efforts to understand their recent evolutionary history; growing evidence among several caiman species suggests that hybridization is more prevalent than previously thought. Molecular analyses in conjunction with assessments of morphological variation and paleontology are contributing to a more accurate understanding of crocodylian phylogeny, particularly within Crocodylidae and Gavialidae.