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
Short-tailed horned lizard Mexican states of Puebla and Oaxaca. It may also inhabit Veracruz. Short-tailed horned lizard The short-tailed horned lizard ("Phrynosoma braconnieri" ) is an uncommon species of horned lizard endemic to Mexico. It has a very distinct, shortened tail, which is sometimes not apparent. The specific epithet, "braconnieri", is in honor of French naturalist Séraphin Braconnier. "P. braconnieri" has a very short tail relative to its body length, the shortest of the horned lizards, or indeed of any lizard, thus its common name. "P. braconnieri" inhabits pine-oak woodland and xeric thorn-scrub. It can also be found in corn fields or other