Lizard heads called the parietal eye, a basal ("primitive") feature also present in the tuatara. This "eye" has only a rudimentary retina and lens and cannot form images, but is sensitive to changes in light and dark and can detect movement. This helps them detect predators stalking it from above. Until 2006 it was thought that among lizards, only the Gila monster and the Mexican beaded lizard were venomous. However, several species of monitor lizards, including the Komodo dragon, produce powerful venom in their oral glands. Lace monitor venom, for instance, causes swift loss of consciousness and extensive bleeding through its
Slender glass lizard Slender glass lizard The slender glass lizard ("Ophisaurus attenuatus") is a legless lizard in the family Anguidae. The species is endemic to the United States. Two subspecies are recognised. Slender glass lizards have yellow to brown bodies with six stripes, and they have two lateral grooves (one on each side). Unlike snakes, they have eyelids and ears. "O. attenuatus" can attain a total length (including tail) of up to 1 meter (about 40 inches). "O. attenuatus" is found in the United States, from as far north as Wisconsin, east to Virginia, south to Florida, and west to Texas, in grasslands