Members comprising the class Reptilia, having evolved from amphibians to live and reproduce on land, share certain common characteristic adaptations that enabled this success.

• Dry, scaly, protective skin on all or part of their body,
• Lungs and the ability to breathe air,
• Internal fertilization and amniotic development (laying, or gestating internally, a shelled egg),
• An internal skeleton having four limbs, or descended from tetrapod vetrebrate ancestors,
• Claws, if feet are present,
• Most are cold blooded (ectothermic).

The major groups of extant reptiles can be counted on one hand: turtles & tortoises, snakes & lizards, crocodialians, and tuataras.

Testudines (Turtles, Tortoises, Terrapins)

Squamata (Snakes, Lizards)

Crocodilians (Alligators, Crocodiles, ...)

Tuataras (Tuatara)



Because they share a common ancestor with and are more closely related to crocodiians than are other reptiles, some people think that a new group should be included:

Birds!

Turtles & Tortoises

Snakes & Lizards

Crocodilia

Tuatara