Reptiles are a class of air-breathing, cold-blooded vertebrates that have scaly bodies rather than hair or feathers. They are characterized by the following features:

• Skin: Reptiles have skin covered in a horny epidermis, making it watertight and enabling them to live on dry land. Their skin is also covered in scales, bony plates, or a combination of both.

• Temperature regulation: Unlike birds and mammals, reptiles do not maintain a constant internal body temperature. They rely on heat from their surroundings to warm up and move into the sun or shade as needed.

• Reproduction: Most reptile species are egg-laying, though certain species give birth to live young. Only boas and pythons give birth to live young, while the other species lay their eggs in a simple nest and leave.

• Vertebrates: Reptiles have backbones and are classified as tetrapod vertebrates, creatures that either have four limbs or are descended from four-limbed ancestors.

• Lungs: Reptiles have lungs for breathing.

• Amniotic development: Reptiles have internal fertilization and amniotic development.

The class Reptilia includes lizards, snakes, turtles, alligators, and crocodiles. However, to be genetically consistent, it should also include birds, since crocodilians are more closely related to birds than to lizards, snakes, or turtles.