Archosaurier

Archosauria, or archosaurs, is a group of diapsid reptiles that includes all living birds and crocodilians, as well as the extinct non-avian dinosaurs and pterosaurs. The archosaurs first appeared in the late Permian period and became the dominant terrestrial vertebrates during the Mesozoic Era. The name archosauria means “ruling lizards” in reference to their evolutionary success.

Typical archosaurs show skull openings such as the antorbital fenestra in front of the eyes and a mandibular fenestra in the jaw, a generally more rigid skull arrangement, and a posture that tends toward upright limbs with an adapted ankle joint that improved locomotion on land. These features helped archosaurs occupy a wide range of ecological roles during their long history.

Within Archosauria, two major lineages are recognized: Avemetatarsalia, which includes dinosaurs, birds, and pterosaurs, and Pseudosuchia, which includes crocodilian lineages and their extinct relatives. The Triassic period saw rapid diversification, giving rise to the two major branches that would dominate the terrestrial and aerial ecosystems of the following eras; many archosaurs went extinct by the end of the Cretaceous, while birds and crocodilians survived into the present.

Today archosaurs are represented by two living clades: Aves (birds) and Crocodylia (crocodilians). They are distinguished from lepidosaurs (lizards and snakes) by differences in skull openings, ankle structure, and other skeletal features associated with their erect posture and distinctive evolutionary innovations.