Crocodylomorpha: Overview

The tropical Indo-Pacific apex predator Crocodylus porosus awaits its next meal. Males can easily grow to over 5 meters in length; before the coming of the white man, they were even larger Photograph by Lepidlizard, Public Domian, Wikimedia

This unit is about the crocodiles, alligators, and their cousins and ancestors; in Linnaean taxonomy the Order Crocodilia [1]; in Cladistic nomenclature the Clade Crocodylomorpha (it doesn't matter what name we give them because both name smean the same). This very successful reptilian lineage includes is every bit as ancient as the dinosaurs (to which they are often compared). It includes everything from lightly built and even bipedal Sphenosuchia which rather resembled miniature dinosaurs and were previously refered to under the rubric of "pseudosuchians" ("false crocodiles") [2], to ocean going Metriorhynchids as well adapted to marine existence as any ichthyosaur or dolphin, to an extraordinary diversity of fully terrestrial forms, to narrow-snouted fish eaters and broad-muzzled semi-aquatic apex preditors, the largest of which - such as Sarcosuchus and Deinosauchus - surpassed in size even the carcharodontosaur and tyrannosaur theropod dinosaurs. At the other end of the size scale, some Jurassic crocodiles were no bigger than medium-sized lizards. MAK120201 120302

Notes

[1] More usually but incorrectly spelled Crocodylia with a "y" (see e.g. Carroll 1988 for only one authoritative textbook that usues this spelling). The original spelling used by Richard Owen (1842), the first to scientifically describe the group was Crocodilia. Crocodylia is incorrectly attributed to Laurenti 1768 (based on his naming of the genus Crocodylus) and Gmelin 1789 - Paleobiology Database. More recently, Crocodylia has been used in cladistics in a much more limited context to refer to the crown group crocodiles, and Crocodylomorpha to the stem group, which is directly equivalent to the evolutionary systematic Crocodylia (=Crocodilia). Actually Crocodylia is simply the nested clade within Crocodylomorpha. MAK120302

[2] In his pioneering work on cladistic paleontology, Gauthier (1986) used this term to refer to the clade to refer to Crocodiles and all other archosaurs closer to them than to birds. Thus true crocodiles are included under the heading of "false crocodiles". Perhaps because of this incongruance, Paul Sereno rejected the term Pseudosuchia and instead uses Crurotarsi (which we have also adopted).