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
Philippine sailfin lizard sailfin lizards were commonly available in the United States during the 1990s, but today they are now rare and expensive in the United States (costing about $650 for a captive bred juvenile). Breeding in captivity has only been done in a few cases. But because it is common in many parts of the Philippines, the pet trade in many regions still continues and some are even unrecognized by the government. Philippine sailfin lizard The Philippine sailfin lizard, crested lizard, sail-fin lizard, sailfin water lizard, soa-soa water lizard (Hydrosaurus pustulatus) or its native name "ibid" is an oviparous lizard living only