Archosauriformes

Archosauriformes is a clade of diapsid reptiles that developed during the late Permian period. The group includes all archosaurs – a group that comprises modern birds and crocodiles, as well as extinct dinosaurs and pterosaurs – and several extinct forms more closely related to archosaurs than to other living reptiles. The earliest archosauriforms, such as Proterosuchus, appeared in the Late Permian. They flourished during the Mesozoic era, which is often known as the "Age of Dinosaurs".

Characteristics

Archosauriformes are characterized by several distinct features, including antorbital and mandibular fenestrae (openings in the skull) and serrated teeth. They also have a unique ankle joint, in which the astragalus bone is fixed to the tibia, forming a hinge. This is known as the "crocodile-normal" ankle and is found in crocodilians and their extinct relatives.

Evolution and Phylogeny

The Archosauriformes lineage traces back to the late Permian period, around 250 million years ago. The group survived the Permian–Triassic extinction event, which wiped out over 90% of marine species and 70% of terrestrial vertebrate species. The archosauriforms diversified during the Triassic period, giving rise to the archosaurs.

The phylogeny of Archosauriformes is complex and has been the subject of much debate. The group is usually divided into two main clades: the Archosauria, which includes birds, crocodiles, dinosaurs, and pterosaurs, and the Proterosuchidae, which includes several extinct forms more closely related to archosaurs than to other living reptiles.

Extinct Groups

Several groups of extinct archosauriforms are known, including the Proterosuchidae, Erythrosuchidae, and Euparkeriidae. These groups were diverse and included both carnivorous and herbivorous forms. Some, like the proterosuchids, were among the earliest archosauriforms and were characterized by long, slender bodies and elongated snouts.

See Also

• Archosauria
• Proterosuchidae
• Erythrosuchidae
• Euparkeriidae
• Permian–Triassic extinction event