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
Sicilian wall lizard Sicilian wall lizard The Sicilian wall lizard ("Podarcis waglerianus") is a species of lizard in the family Lacertidae. Endemic to Italy, it occurs in Sicily and the Aegadian Islands. Its natural habitats are temperate forests, temperate shrubland, Mediterranean-type shrubby vegetation, temperate grassland, arable land, pastureland, and rural gardens. The IUCN does not consider it to be a threatened species. Three subspecies are recognized: "P. w. antoninoi", "P. w. marettimensis" and "P. w. waglerianus". The specific name, "waglerianus", is in honor of German herpetologist Johann Georg Wagler. The Sicilian wall lizard grows to a length of about with males being slightly