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
Giant plated lizard Giant plated lizard The giant plated lizard ("Gerrhosaurus validus") is a lizard of the Gerrhosauridae family, which is found in dry to mesic habitats of southern Africa. They are wary and stay close to their rocky retreats. A large lizard with a flattened head and body, its length is a maximum of . The soles of the feet have black rubber-like balls, an adaptation to living on rock outcrops. It is called the plated lizard because of the platelike scales on the back. This lizard is very shy and hard to approach. When threatened, it will jam itself into rock