Reptiles
Reptiles, or members of the class Reptilia, are air-breathing, cold-blooded vertebrates that have skin covered in scales as opposed to hair or feathers. They are tetrapods (having or having descended from vertebrates with four limbs) and amniotes, whose embryos are surrounded by an amniotic membrane. Modern reptiles inhabit every continent with the exception of Antarctica, and four living orders are currently recognized:
- Crocodilia (crocodiles, gavials, caimans, and alligators): 23 species
- Sphenodontia (tuatara from New Zealand): 2 species
- Squamata (lizards, snakes, and amphisbaenids ("worm-lizards"): approximately 7,900 species
- Testudines (turtles, tortoises, and terrapins): approximately 300 species
The majority of reptile species are oviparous (egg-laying) although certain species of squamates are capable of giving live birth.