The first definition of Crocodylia was given by Brochu (1999:13). Several authors prior to Brochu (1999) refer to crown crocdilians, but these references fall short of the minimum for a complet phylogenetic definition. A crown clade, it should be kept in mind, need not have a node-based definition (Sereno 2005); even if node-based it may have different specifiers. Thus, although Benton and Clark (1988) limited Crocodylia to “crown group” crocodiles, they did not provide a specific definition (contra Brochu 1999:13). Similarly, Clark (1994:84) recognized Crocodylia as “including only the closest relatives of extant Crocodylia (the crocodylian crown-group).”

Brochu (1999) defined Crocodylia as “the last common ancestor of alligatorids, crocodylids, and gavialoids, and all of its descendants.” Sereno (2001) used Gavialis gangeticus and Crocodylus niloticus as specifiers; Brochu (2003) refers to all three subclades by species, a textual variant of which is adopted here as the active definition. It is better to include Alligator mississippiensis, given alternative phylogenies that place Alligatoroidea as the basal sister taxon to other crocodylians (Densmore 1983, Buffetaut 1985).