A reptile is any animal of the class Reptilia, i.e. air-breathing, cold-blooded, usually scaly and typically egg-laying. There are over 8,000 species, which inhabit every continent except Antarctica. The class is divided into four orders: Squamata (including lizards and snakes); Testudines (including turtles); Crocodylia (including crocodiles); and Sphenodontida (tuataras).