Dinosauria

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See Dinosauria in Wikipedia, the free encyclopedia.

Dinosauria, Sir Richard Owen (1841), sensu Padian & May (1993), "Fearfully Great Lizards" or "terrible lizards"

Superorder Dinosauria, including birds, is the single most successful terrestrial vertebrate group in the history of life, and is defined as the common ancestor of orders Saurischia and Ornithischia and all its descendants. Dinosaurs belong to the class Sauropsida (reptiles) and the sublcass Diapsida.

1 Features
2 Origins
3 References
4 Acknowledgments

Features

Synapomorphies underwriting the holophyly of this unranked clade include (after The Dinosauria, ed. Weishampel, Dodson & Osmolska, 1990):

Vomers reach caudally to the antorbital fenestra at least
Three or more sacral vertebrae present
Scapulocoracoidal glenoid oriented backward
Deltopectoral crest low and 1/3 or 1/2 the length of the humerus
Three of fewer phalanges in the fourth manual digit
Acetabulum completely perforate
Proximal head of femur fully offset, conferring parasagittal gait
Fibula reduced
Ascending process of the astragalus well developed

Origins

Archosauromorpha is an infraclass of diapsids that likely descended from a single common ancestor about 260 to 250 million years ago. The Archosauriformes developed from archosauromorph ancestors about 250 million years ago. They include the family Proterosuchidae which gave rise to the Erythrosuchidae who in turn evolved into the Archosaurs about 250 to 245 million years ago. Ornithodira is a clade within Archosauria that existed from about 245 to 228 million years ago. Ornithodires diversified to produce dinosaurs about 230 million years ago.