Class Reptilia
There are approximately 8,655 species of living reptiles found in four orders:
1. Sphenodontida – tuatara
2. Squamata – lizards and snakes
3. Chelonia - turtles and tortoises
4. Crocodilia – crocodiles

Reptiles (class Reptilia) are members of a class of air-breathing, ectothermic (cold-blooded) vertebrates which are characterized by laying shelled eggs (except for some vipers and constrictor snakes that give live birth), and having skin covered in scales and/or scutes.

They are tetrapods, either having four limbs or being descended from four-limbed ancestors. Modern reptiles inhabit every continent with the exception of Antarctica, and four living orders are currently recognized

There is some debate about which animals fall into the Class Reptilia or even if it should still
exist. The discovery of the close link between reptiles and birds led some authorities to argue
that Class Aves should be abolished and the birds considered as part of the group Dinosauria.
However it seems that the modern avian characteristics of feathers and oviparity (egg-laying)
shared by all birds make them unique enough to remain in their own class, Aves. Nevertheless
this does indicate that class Reptilia is paraphyletic rather than monophyletic. This means that,
since it does not include birds, the “Reptilia” categorization does not include all descendants of
the most recent common ancestor. The argument about where to place birds could continue for
some time. The Academy includes tuataras, lizards, snakes, turtles, and crocodilians in the
Class Reptilia.
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