name for the dry-skinned, usually scaly, cold-blooded vertebrates (see Chordata) of the order Reptilia. Reptiles are found in a variety of habitats throughout the warm and temperate regions (except on some islands), with the greatest variety in the tropics. Reptiles differ from other terrestrial vertebrates (birds and mammals) in that they are cold-blooded, that is, they lack an effective system for regulating their body temperature, which tends to approach that of the environment. For this reason reptiles are not found in the coldest regions of the world, and they hibernate in cool winter areas.
Living reptiles are classified in four orders. The turtles, order Chelonia, have a protective bony shell, usually covered with horny plates. They are mostly aquatic in habits although some (see tortoise) are adapted to land. They are the oldest living reptiles, having existed nearly unchanged since the Triassic period. Members of the order Crocodilia, which includes alligators, caimans, crocodiles, and gavials, are large, carnivorous reptiles of tropical and subtropical swamps and rivers. They constitute the only remaining order of the great reptilian subclass Archosauria, or ruling reptiles, which includes the extinct dinosaurs. The order Squamata includes the lizards (suborder Sauria) and snakes (suborder Serpentes). Nearly all members of this large and successful modern order are terrestrial. The order Rhynchocephalia has a single living member, the tuatara, a lizardlike reptile of New Zealand.
Reptiles first evolved from amphibians about 250 million years ago in the Carboniferous period and were dominant in the world's fauna during the Mesozoic era, sometimes called the Age of Reptiles. The dinosaurs, the marine Ichthyosaurus and Plesiosaurus, and the flying pterosaurs reached the peak of their development and distribution in the later part of this era (late Cretaceous period). Mammallike reptiles appeared very early in reptilian history and by the Triassic period had given rise to mammals. Bird ancestors arose from precursors of the dinosaurs; the first known birds lived in the Jurassic. The only reptiles that survived into the Cenozoic era belonged to the presently living orders. The approximately 6,000 living reptile species represent a very small fraction of this once vast class.
- See Field Guide to Reptiles and Amphibians (1958). ,
- A. Bellairs, The Life of Reptiles (2 vol., 1970).
- K. P. Schmidt and R. F. Inger, Living Reptiles of the World (1957, repr. 1972).
- Reptiles of North America (1982). ; ,
- Reptiles and Amphibians (1987). ; ,
A vertebrate animal belonging to the class Reptilia (about 6000 species), which includes crocodiles , turtles , lizards , snakes , and...
Any of c .6,000 species of vertebrates distributed worldwide. Reptiles are cold-blooded. Most lay eggs on land. Some species - particularly ...