Posted: 10 April 2001

Common name applied to members of the vertebrate class Reptilia, which includes snakes, lizards, turtles, crocodilians, the tuatara, and numerous extinct fossil species. Among the existing forms are about 2,500 species of snakes, 3,000 of lizards, nearly 250 of turtles and tortoises, and 21 species of crocodilians. They are distributed throughout the temperate and tropical regions of the world; being cold-blooded (dependent on the environment for warmth; see below), very few reptiles can develop or live in colder regions.