Any of the approximately 6,000 species of the class Reptilia, air-breathing
Most species have short legs (or none) and have long tails, and most lay eggs. Living reptiles include the scaly reptiles ( snakes and lizards ; order Squamata), the crocodiles (Crocodilia), the turtles (Chelonia), and the unique tuatara (Rhynchocephalia). Being cold-blooded, reptiles are not found in very cold regions, and in regions with cold winters they usually hibernate. They range in size from geckos that measure about 1 in. (3 cm) long to the python , which grows to 30 ft (9 m); the largest turtle, the marine leatherback, weighs about 1,500 lbs (680 kg). Extinct reptiles include the {{link=dinosaur">dinosaurs , the pterosaurs , and the dolphinlike ichthyosaurs.