Lizard | Tortoise
Reptiles are air-breathing, cold-blooded vertebrates that have scaly bodies as opposed to hair or feathers; they represent an intermediate position in evolutionary development between amphibians and warm-blooded vertebrates, the birds and mammals. They are tetrapods and amniotes whose embryos are surrounded by an amniotic membrane, and members of the class Sauropsida inhabiting every continent with the exception of Antarctica. Today they are represented by four orders:
* Crocodilia (crocodiles, gharials, caimans and alligators): 23 species
* Sphenodontia (tuataras from New Zealand): 2 species
* Squamata (lizards, snakes and amphisbaenids ("worm-lizards"): approximately 7,900 species
* Testudines (turtles and tortoises): approximately 300 species
The majority of reptile species are oviparous (egg-laying) although certain species of squamates are capable of giving live birth. This is achieved, either through ovoviviparity (egg retention), or viviparity (offspring born without use of calcified eggs). Many of the viviparous species feed their fetuses through various forms of placenta analogous to those of mammals with some providing initial care for their hatchlings.