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
The Lizard main units; the serpentinites, the "oceanic complex" and the metamorphic basement. Several nature sites exist on the Lizard Peninsula; Predannack nature reserve, Mullion Island, Goonhilly Downs, and the Cornish Seal Sanctuary at Gweek. An area of the Lizard covering is designated a national nature reserve because of its coastal grasslands and heaths and inland heaths. The peninsula contains 3 main Sites of Special Scientific Interest (SSSI), both noted for their endangered insects and plants, as well as their geology. The first is East Lizard Heathlands SSSI, the second is "Caerthillian to Kennack SSSI" and the third is West Lizard SSSI,