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
Northern caiman lizard which many other lizards apparently fail to and can generally recognize their owners, given they have been kept for the right amount of time and are in good health. Captive diet includes turkey meat (often mixed with Mazuri alligator diet), mussels, clam meat, catfood, fish and some fruits. Northern caiman lizard The northern caiman lizard, "Dracaena guianensis", is a species of lizard found in northern South America. The caiman lizard is built similarly to its cousin the tegu, with a large heavy set body and short but powerful limbs. Its head is bulky and often a red or orange color.