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
Spineless forest lizard Spineless forest lizard The spineless forest lizard, crestless lizard or lionhead agama (Calotes liocephalus) is a species of lizard in the family Agamidae. It is endemic to Sri Lanka. "Calotes liocephalus" grows to in snout–vent length and in total length. Spineless forest lizard is one of four "Calotes" species endemic to Sri Lanka, which all share a common set of characteristics. These include a relatively short head, with swollen cheeks, backwards, or backwards and downwards pointing scales on the side of the body, a tail that is strongly swollen at the base in fully grown adult males. This lizard is