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Mounted skeletons of Tyrannosaurus (left) and Apatosaurus (right) at the AMNH. Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago, although the exact origin and timing of the evolution of dinosaurs is the subject of active research.
Dinosaur classification began in 1842 when Sir Richard Owen placed Iguanodon, Megalosaurus, and Hylaeosaurus in "a distinct tribe or suborder of Saurian Reptiles, for which I would propose the name of Dinosauria." [1] In 1887 and 1888 Harry Seeley divided dinosaurs into the two orders Saurischia and Ornithischia, based on their hip structure. [2]
Dinosaurs are a diverse group of reptiles [note 1] of the clade Dinosauria. They first appeared during the Triassic period , between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is a subject of active research.
List of Asian dinosaurs; List of Australian and Antarctic dinosaurs; List of dinosaurs and other Mesozoic reptiles of New Zealand; List of European dinosaurs; List of Indian and Madagascan dinosaurs; List of North American dinosaurs. List of Appalachian dinosaurs; List of archosaurs of the Chinle Formation; List of dinosaurs of the Morrison ...
Archosaurs are a group of diapsid amniotes whose living representatives consist of birds and crocodilians. This group also includes all extinct dinosaurs, extinct crocodilian relatives, and pterosaurs. [74] [75] [76]
A Brazilian scientist has identified fossils of a small crocodile-like reptile that lived during the Triassic Period several million years before the first dinosaurs. The fossils of the predator ...
The latter group are often referred to as mammal-like reptiles, but should be termed protomammals, stem mammals, or basal synapsids, because they are not true reptiles by modern cladistic classification. They were the dominant land vertebrates throughout the Permian, but most perished in the Permian–Triassic extinction event.
Named Gondwanax paraisensis, the four-legged reptile species was roughly the size of a small dog with a long tail, or about 1 meter (39 inches) long and weighing between 3 and 6 kg (7 to 13 pounds ...