Archosauriformes

Archosauriformes (Greek for 'ruling lizards', and Latin for 'form') is a clade of diapsid reptiles encompassing archosaurs and some of their close relatives. It was defined by Jacques Gauthier (1994) as the clade stemming from the last common ancestor of Proterosuchidae and Archosauria. Phil Senter (2005) defined it as the most exclusive clade containing Proterosuchus and Archosauria. Gauthier as part of the Phylonyms (2020) defined the clade as the last common ancestor of Gallus, Alligator, and Proterosuchus, and all its descendants. Archosauriforms are a branch of archosauromorphs which originated in the Late Permian (roughly 252 million years ago) and persist to the present day as the two surviving archosaur groups: crocodilians and birds.

Archosauriforms present several traits historically ascribed to the group Archosauria. These include serrated teeth set in deep sockets, a more active metabolism, and an antorbital fenestra (a hole in the skull in front of the eyes). Reptiles with these traits have also been termed "thecodonts" in older methods of classification. Thecodontia is a paraphyletic group, and its usage as a taxonomic category has been rejected under modern cladistic systems. The name Archosauriformes is intended as a monophyletic replacement compatible with modern taxonomy.