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File:800px-Europasaurus holgeri Scene 2.jpg
Painting of a late Jurassic Scene on one of the large island in the Lower Saxony basin in northern Germany. It shows an adult and a juvenile specimen of the sauropod Europasaurus holgeri and Iguanodons passing by. There are two Compsognathus in the foreground and an Archaeopteryx at the right.
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. They existed during the Mesozoic era of earths prehistory, and went extinct around 65 million years ago as a result of one or more astroid impacts.



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

Origins and Evolution

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. Many scientists once believed dinosaurs were polyphyletic with multiple groups of unrelated "dinosaurs" evolving due to similar pressures, but dinosaurs are now known to have formed a single group.

The dinosaurs began to occupy a prominent role in earth's ecosystem after the Triassic-Jurassic extinction event when most of the other groups of early archosaurs went extinct, which allowed the dinosaurs to evolve and fill the ecological niches left by the extinct archosaur species.




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