Thalattosuchia

Thalattosuchia is the name given to a clade of marine crocodylomorphs from the Early Jurassic to the Early Cretaceous that had a cosmopolitan distribution. They are sometimes colloquially referred to as marine crocodiles or sea crocodiles, though they are not actually members of Crocodilia.

The term Thalattosuchia was coined by Fraas in 1901. Various authors have considered Thalattosuchia to be either an infraorder or a suborder within "Mesosuchia". However, the term "Mesosuchia" is a paraphyletic group, and as such is no longer used. For consistency, the Thalattosuchia are here placed at suborder rank although the order that contains it is presently unnamed. Since Buffetaut (1982) demonstrated the shared characteristics of the early forms of Metriorhynchidae and Teleosauridae, Thalattosuchia has consisted of these two families. Some of the early members of Teleosauridae have been discovered in non-marine deposits suggesting thalattosuchians 'moved' from being semi-aquatic freshwater forms to fully-marine forms. The systematics of the genus Pelagosaurus are confused, with differening topologies placing it as either a teleosaurid, or as the sister taxon to a Teleosauridae + Metriorhynchidae clade. Other authors have considered Pelagosaurus to be a basal metriorhynchid.