A glass lizard is a lizard of the genus Ophisaurus, of which there are about 15 species. Most species of glass lizard are native to Asia, but some live in North America and at least one species, Ophisaurus koellikeri , is native to North Africa. The glass lizard is unusual because it resembles a snake, as most species do not have legs. Other common names for the glass lizard include glass snake and jointed snake.
It may be surprising to learn that it is not the existence of legs that marks the difference between a snake and a lizard. While many people may not be able to tell the difference between a glass lizard glimpsed in the garden and a snake, a number of physical characteristics, including the shape of the head, make the glass lizard officially a lizard. The animal also has movable eyelids and external ear openings, two features absent from snake anatomy.
The glass lizard gets its name from its habit of breaking its tail into many pieces, resembling shattered glass, when threatened by a predator. The pieces all continue moving to distract the predator while the glass lizard makes its escape. Rebuilding a tail afterwards requires a great deal of energy, and the new tail is often smaller than the first.
Glass lizards are carnivorous, with a diet consisting of insects, arthropods, and sometimes small mammals or birds, depending on the size of the glass lizard. Since they cannot unhinge their jaws like snakes, glass lizards cannot eat anything much larger than their head. The largest glass lizards exceed four feet (122 cm) in length.
One of the largest glass lizards is the Scheltopusik of Southern Europe, which resembles a giant earth-worm. It sometimes has two small legs near the end of its body and is unlikely to drop its tail, since its large size allows it to defend itself. The Scheltopusik is sometimes kept as an exotic pet.