archosauriformes

Archosauriformes is a clade of diapsid reptiles that includes Archosauria (the archosaurs, comprising birds and crocodilians and their extinct relatives) and a variety of early, more basal lineages. The group sits within the larger Archosauromorpha and is defined as all species more closely related to archosaurs than to lepidosaurs, including both the crown group Archosauria and several stem archosauriforms such as Proterosuchidae and Euparkeriidae.

Fossil evidence shows that archosauriforms first appeared in the Early Permian, with a broad geographic distribution. They became a dominant exploratory group during the Triassic, contributing to the early diversification of archosauromorph reptiles after the Permian–Triassic extinction. Members occupied a range of ecological niches, from small terrestrial predators to larger forms, and they show a progression of skull and skeletal features that culminate in the conditions seen in crown archosaurs.

Morphology commonly includes distinct skull openings, notably the presence of an antorbital fenestra in many members, and several skeletal traits that facilitated a more erect gait and versatile locomotion. Over time, archosauriforms gave rise to archosaurs, whose lineages include the non-avian dinosaurs, pterosaurs, crocodilians, and birds. The study of Archosauriformes illuminates the early evolutionary steps leading to the archosaurian body plan and the eventual rise of dinosaurs and their relatives.

See also: Archosauria, Euparkeriidae, Proterosuchidae, Archosauromorpha.