Description
In length, lizards range from the half inch (1.5 cm) of the smallest gecko to the more than 10 feet (3 m) of the dragon of Komodo. In weight, they range from 5 ounces (140 g) to more than 250 pounds (113 kg). A number of lizards are shaped like toads with short tails, and others like snakes and worms. Most have well-defined heads and necks, elongated bodies, and tapering tails. Most lizards have four limbs, each ending in five clawed toes. Some have only vestiges (traces) of limbs in their skeletons.
A typical lizard has a small, disc-shaped organ called the pineal body on top of its head. Nerve tissue extends from this organ to the brain. Research suggests that the pineal body helps regulate the lizard's biological clock.
In many species, the lizard's tail will easily break off from the body, allowing the animal to escape if seized by the tail. The lizard will grow a new tail, which will usually be shorter than the old and will contain a gristly rod or tube instead of bone. A new tail will grow also from a break in the tail. That is why some lizards have two or three tails.
A lizard has scaly skin. The scales are sometimes grainy, spiny, or beadlike. From time to time the lizard sheds its outer skin. Some lizards are brightly colored, but most are colored in dull shades that match their backgrounds. Chameleons and some others can change color to a limited extent.
Almost all lizards have two ear holes and two eyes with movable lids. In those lacking eyelids, the eye is protected by a transparent membrane. Lizards have fairly good hearing and sight, and they can see colors. The chameleon can move each eye independently.
The tongue of an insect-eating lizard is long and covered at the end with sticky saliva. It can be swiftly thrust out to catch insects. A number of lizards have forked tongues that aid in smelling. The tongue is flicked out and in to carry odor-bearing particles to the smelling organs on the roof of the mouth.
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