Archosauromorpha

Archosauromorpha is a major lineage of reptiles that includes archosaurs—crocodilians and birds—and extinct relatives such as pterosaurs and plesiosaurs.

Sauropsida: The amniote lineage that includes reptiles and birds, traditionally distinguished from mammals. Archosauromorpha is one major branch within this broader amniote lineage.
Antorbital fenestra: An opening in the skull in front of the eye socket, characteristic of many archosauriforms. This skull opening is a defining feature of many derived members of the lineage.
Protorosaurus: An extinct Late Permian reptile often regarded as one of the earliest archosauromorphs. It represents an early stage in the fossil history of the group.
Permian–Triassic extinction event: A mass extinction about 252 million years ago that eliminated most marine species and many terrestrial groups. Archosauromorphs diversified in the ecological aftermath of this extinction.
Diapsid: A reptile defined ancestrally by two openings on each side of the skull behind the eye. Archosauromorphs belong within the diapsid radiation.
Temporal fenestra: An opening in the skull behind the eye that provides space for jaw muscles. Diapsid skull openings are part of the anatomical framework used to classify archosauromorphs.
Tanystropheus: An extinct Triassic reptile known for an exceptionally elongated neck supported by specialized vertebrae. Its unusual proportions illustrate the ecological experimentation of early archosauromorphs.
Triassic: The geologic period from about 252 to 201 million years ago, following the Permian. Many major archosauromorph branches became prominent during this period.
Lepidosauromorpha: The reptile lineage that includes tuatara, lizards, snakes, and their extinct relatives. It is the principal diapsid branch contrasted with Archosauromorpha.
Erect limb posture: A posture in which the limbs extend beneath the body rather than sprawling sideways. Upright limb support evolved in several archosauromorph branches and enabled varied locomotion.

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