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
Ocellated lizard Ocellated lizard The ocellated lizard, eyed lizard or jeweled lacerta in the pet trade ("Timon lepidus") is a species of wall lizard also known as the (, ). "Timon lepidus" is one of the largest members of its family. The adult is long and may reach up to , weighing more than . About two-thirds of its length is tail. Newly hatched young are long, excluding tail. This is a robust lizard with a serrated collar. The male has a characteristic broad head. It has thick, strong legs, with long, curved claws. The dorsal background colour is usually green, but