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
Leaf-nosed lizard Leaf-nosed lizard Ceratophora tennentii, commonly known as the horned lizard, horn-nosed lizard, leaf-nosed lizard, and Tennent's leaf-nosed lizard, is a species of lizard in the family Agamidae. The species is endemic to Sri Lanka. The generic name, "Ceratophora", means horn bearer. The specific name, "tennentii", is in honour of Irish politician James Emerson Tennent, who was Colonial Secretary of Ceylon (1845–1850). "C. tennentii" has a leaf-like appendage on the end of its nose. The species can reach lengths of over including the tail. Males usually have more green in their coloration than females have, although they can change color to