What are the Major Groups of Reptile?
Reptiles, also known as Class Reptilia, Class Sauropsida, or merely sauropsids, are ectothermic (“cold-blooded” — though this term has now fallen out of fashion) animals covered in scales. There are over 8,200 reptile species, about 50% more than their relatives, the mammals. The reptile is one of the few taxonomic classifications among tetrapods that are polyphyletic — meaning the group deviates from the convention of including all descendants of a common ancestor. Birds are actually descendants from ancient reptiles, the dinosaurs, but are not considered reptiles. If birds were included in Reptilia, the group would be monophyletic. Reptiles are one of two amniote groups, the other being the synapsids, represented today by the mammals. Amniotes nurture their embryos using a series of complex membranes. By contrast, amphibians, that is, non-amniotes, have simple eggs that must be laid in water. Reptiles and the ancestors of mammals, the synapsids, split from each other a very long ti
