Dinosauria

Dinosauria is a group of archosaur reptiles that includes birds and the extinct non-avian dinosaurs. Its members are distinguished by characteristic features of the pelvis and hind limbs.

Archosauria: A major reptile group that includes crocodilians, pterosaurs, and dinosaurs, including birds. Dinosauria is one branch of this larger group of reptiles.
Dinosaurian pelvis: The distinctive pelvic structure found in dinosaurs, including a perforated hip socket and characteristic joint arrangements. Pelvic anatomy supplies key traits for identifying dinosaur fossils and relationships.
Tyrannosaurus rex: A large Late Cretaceous theropod dinosaur known from western North America. Its fossils exemplify the large-bodied predatory dinosaurs within Theropoda.
Nyasasaurus: A Middle Triassic reptile from Tanzania whose fragmentary remains may represent an early dinosaur or close relative. Its uncertain placement bears on how early Dinosauria originated and diversified.
Cretaceous–Paleogene extinction event: A mass extinction about 66 million years ago that eliminated non-avian dinosaurs and many other organisms. It ended non-avian dinosaur lineages while birds survived.
Ornithodira: A group of archosaurs that includes pterosaurs and dinosaurs, including birds. This broader grouping places dinosaurs among their closest archosaur relatives.
Mesotarsal ankle: An ankle joint in which movement occurs mainly between the astragalus and the remaining foot bones. This ankle arrangement is among the skeletal traits associated with early dinosaurs.
Triceratops: A large, horned ceratopsian dinosaur from the Late Cretaceous of North America. Its skull and frill show the distinctive diversity of ornithischian dinosaurs.
Eoraptor: A small Late Triassic dinosaur from Argentina, represented by a nearly complete skeleton. Its early age and anatomy illuminate the diversity of dinosaurs near their origin.
Avian dinosaurs: The dinosaur lineage comprising birds and their extinct bird-like relatives. Birds preserve one branch of Dinosauria beyond the end-Cretaceous extinction.

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