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
Banded rock lizard Banded rock lizard The banded rock lizard ("Petrosaurus mearnsi" ) is a species of lizard in the family Phrynosomatidae. The species is native to western North America. The specific name, "mearnsi", is in honor of American naturalist Edgar Alexander Mearns, who collected the first specimens. "P. mearnsi" is endemic to extreme southern California and Baja California, Mexico. It also occurs on Isla El Muerto. "P. mearnsi" is an extremely flat-bodied lizard. Its dorsum is olive, brown or gray, with white or bluish spots. It has a single black collar, a banded tail, and granular scales on its body, with keeled