Lizards are scaly-skinned animals which usually have four legs and a tail, movable eyelids, visible ear openings, claws and toothed jaws. A few species are legless and superficially resemble snakes. They represent the largest group of living reptiles and range in size from tiny skinks to the giant 10 foot-long monitor lizards of Indonesia. Over 3,000 species are found worldwide, 95 of which occur in the U.S. Most lizards lay eggs on or in the ground. The incubation period depends largely on the ambient temperature and the hatchlings are independent from birth. In a few species, the female retains the eggs until the young are ready to hatch.