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Shape
and Size
Reptiles possess three types of body form. The basic type is the lizard-like shape. In this form, ground, wall and tree trunk dwelling reptiles are flattened dorsoventrally, which facilitates concealment and movement. The crocodiles, monitor lizards and geckos are examples of this type of body shape. The legs are well developed. In arboreal forms the body is flattened laterally as in chameleon and the garden lizard, calotes.
In the second type, the body is elongated and cylindrical as in many skinks and all the snakes; legs may be rudimentary or absent.
In the third type, the turtles, and tortoises, the trunk has become rigid and enclosed in a body shell.
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The reptiles form one among the four classes of terrestrial or land dwelling vertebrates or animals with backbone. They have evolved from the amphibians, whose present day representatives are the frogs, toads, newts and caecilians and they have given rise to the birds and mammals. The history of reptiles goes back millions of years. On the basis of fossil evidence, they are believed to have originated during the geologic period known as the upper Carboniferous or Pennsylvanian period 300 to 260 million years ago.
