1. They are mostly terrestrial animals and their body is covered by dry, and cornified skin with epidermal scales or scutes.
2. Reptiles have three chambered heart but four chambered in crocodiles.
3. All are cold blooded amniotes.
4. Most reptiles lay cleidoic eggs with extraembryonic membranes like amnion, allantois, chorion and yolk sac.
5. Excretion : metanephric kidneys and are uricotelic.
6. They are monoecious.
7. Internal fertilization takes place and all are oviparous. eg. Calotes (Garden Lizard), Draco (Flying Lizard), Crocodilus (Crocodile).