Cope (1869) established this group to include a broad range of taxa, including crocodiles, dinosaurs, “thecodonts,” dicynodonts, dinocephalians, rhyncosaurs, and sphenodontids. Later, this taxon was essentially abandoned by Osborn (1903), who dispersed dinosaurs, crocodiles, and other archosaur taxa into separate groups among the Diapsida. Huene (1914) and especially Romer (1933, 1956) re-established Archosauria as a taxon encompassing crocodiles, dinosaurs, pterosaurs, and “thecodonts,” a view that has widely been followed since.
Benton (1985, 1999) coined the taxa Neoarchosauria and Avesuchia, respectively, for a slightly more restricted subgroup within Archosauria that excludes Erythrosuchidae, Proterochampsidae and Euparkeriidae (preferring to use Archosauria for a group based on the presence of an antorbital fenestra). Although Benton (2004:8) refers to a form-qualified definition (”apomorphy-based”) for Archosauria, the phrase he used does not represent a complete phylogenetic definition with at least one specifier (”those diapsids that possess an antorbital fenestra”).
Archosauria was first defined in the abstract of a paper by Gauthier and Padian (1985), based on the unpublished thesis of Gauthier (1984). Archosauria has since been defined multiple times but never with species as specifiers. Sereno (1991) was the first to use formal taxa rather than the vulgar “birds and crocodiles”. The active definition is a first-order revision of all of the preceeding definitions.