| Reptiles are animals in the (Linnaean) class Reptilia. They are characterized by breathing air, laying shelled eggs, and having skin covered in scales and/or scutes. Reptiles are classically viewed as having a "cold-blooded" metabolism. They are tetrapods (either having four limbs or being descended from four-limbed ancestors). Modern reptiles inhabit every continent with the exception of Antarctica, and four living orders are currently recognized: Crocodilia (crocodiles, gavials, caimans, and alligators) Sphenodontia (tuataras from New Zealand) Squamata (lizards, snakes, and worm lizards) Testudines (turtles and tortoises) Amphibians (class Amphibia, from Amphi- meaning "on both sides" and -bios meaning "life"), such as frogs, salamanders, and caecilians, are ectothermic (or cold-blooded) animals that metamorphose from a juvenile water-breathing form, either to an adult air-breathing form, or to a paedomorph that retains some juvenile characteristics. Mudpuppies, for example, retain juvenile gills in adulthood. The three modern orders of amphibians: Anura (frogs and toads), Caudata (salamanders and newts) Gymnophiona (caecilians, limbless amphibians that resemble snakes) |
