Reptiles are vertebrates with scaly, dry, keratinized and thick skin. The skin is periodically sloughed. Some are purely terrestrial while others may be constantly in water. They all breathe via lungs (Burnie, 2003).

There are 8,238 reptile species in the world. In Mexico, 804 species of reptiles have been described and it is considered the country with the second highest diversity of this group after Australia. Gathering amphibians and reptiles together, Mexico possibly ranks number one in the diversity of herpetofauna (Flores-Villela & Canseco-Márquez, 2004).

Reptiles are classified into four orders: crocodiles (Crocodylia), lizards and snakes (Squamata), turtles (Testudines) and tuataras (Sphenodontia). Of these four, the first three are represented in Mexico.

Of the 23 species of crocodiles in the world, four species have been recorded in Mexico: two crocodiles and two alligators.

Of the 381 recorded species of snakes in Mexico, most are colubrids (Colubridae).

Seven of the eight sea turtles of the world live and breed in Mexico. Kemp's Ridley (Lepidochelys kempi) only breeds in Mexico.