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
Common collared lizard Common collared lizard The common collared lizard ("Crotaphytus collaris"), also called eastern collared lizard, Oklahoma collared lizard or collared lizard, is a North American lizard that can reach in length (including the tail), with a large head and powerful jaws. They are well known for the ability to run on their hind legs, looking like small versions of the popular images of theropod dinosaurs. Chiefly found in dry, open regions of Mexico and the south-central United States including Missouri, Texas, Arizona, and Kansas, the full extent of its habitat in the United States ranges from the Ozark Mountains to southern