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
Dunn's spinytail lizard Dunn's spinytail lizard Morunasaurus groi, known commonly as Gro's manticore, Dunn's spinytail iguana, or Dunn's spinytail lizard, is a species of lizard in the family Hoplocercidae. The species is endemic to northwestern South America and Panama. The specific name, "groi", commemorates "Lord Gro", a character in the novel "The Worm Ouroboros" by Eric Rücker Eddison. The tail of "M. groi" is covered with small spines. Males are reddish-brown with dark brown transverse bands across the back, reaching to the middle of the sides and then breaking up into small, irregular dark spots. Small white spots occur between the dark bands