Dinosaur
| Dinosauria Status Extinct | |
|---|---|
| Scientific classification | |
| Orders | |
|
Saurischia Order Sauropodomorpha Order Theropoda Order Ornithischia | |
Dinosaurs were a superorder of reptiles that first appeared approximately 210 million years ago. A few lines of primitive dinosaurs diversified rapidly after the Triassic; the reign of dinosaurs encompassed the ensuing Jurassic, and Cretaceous periods. At the end of the Cretaceous, 65 million years ago, all species of dinosaur became extinct (the Cretaceous-Tertiary extinction event), except for the closely-related line that had already led to the first birds. There is now sufficient evidence to demonstrate that the birds are the descendants of early dinosaurs.
The formal name Dinosauria was first proposed by the English scientist Richard Owen in 1842. The term is a combination of the Greek words deinos ("terrible" or "fearfully great" or "formidable") and sauros ("lizard" or "reptile").
Dinosaurs varied greatly in size. The smallest known species were about the size of a chicken, but most were much larger. The biggest dinosaurs were the Sauropoda; the species Argentinosaurus currently holds the record for the largest land animals ever to live, and were second in size only to certain species of whale.
Saurischians
Saurischians (from the Greek Saurischia meaning "lizard hip") include all the Therapods, bipedal carnivores such as the tyrannosaurs, and sauropods in the dinosaur classification. (brief further characterization is needed here). For more detail, see Saurischia.
Ornithiscians
Many other types of reptiles lived at the same time as the dinosaurs. Some of these are commonly, but incorrectly, thought of as dinosaurs: these include plesiosaurs (which are not closely related to the dinosaurs), and Pterosaurs, which developed separately from reptile ancestors in the late Triassic.
Dinosaurs are divided into two major orders, the Saurischia and the Ornithischia, on the basis of hip structure.
For the most comprehensive family tree of dinosaurs yet available, see
Dinosaurs was also a sitcom television series from Jim Henson Productions.
Warm-blooded dinosaurs
(your text invited)Feathered dinosaurs
(your text is invited)Surmises about dinosaur behavior
(your text in invited)Extinction
The extinction of the dinosaurs is one of the most intriguing problems in paleontology. Only since the 1980s has the nature of this extinction become apparent. The extinction appears to have been rapid, following a period of decreased dinosaur biodiversity, and besides the dinosaurs, other groups, including ammonites, mosasaurs, plesiosaurs, pterosaurs, herbivorous turtles and crocodiles, most kinds of bird, and many groups of mammals, became extinct. The bulk of the evidence now indicates that this extinction event is linked to a bolide impact 65 million years ago, a theory first proposed by Walter Alvarez. The survivors of this mass extinction appear to have been two things that dinosaurs in general were not: small and/or aquatic.Classification of dinosaurs
External links
For the Dinosauria On-Line Dinosaur Omnipedia, with dictionaries of terms, pronunciations, maps and cladograms, see
Active research Museum with 35 complete skeletons and more than 110,000 specimens
This BBC page contains a huge amount of accurate and comprehensible information and pictures
Other Meanings
