Mexican beaded lizard beaded lizard under the Convention on International Trade in Endangered Species as an Appendix I animal, making it illegal to export the species. Mexican beaded lizard The Mexican beaded lizard ("Heloderma horridum") is a species of lizard in the family Helodermatidae, one of the two species of venomous beaded lizards found principally in Mexico and southern Guatemala. It and its congener (member of the same genus) the Gila monster ("Heloderma suspectum") are the only lizards known to have evolved an overt venom delivery system. The Mexican beaded lizard is larger than the Gila monster, with duller coloration, black with yellowish
Mexican beaded lizard three species overlap, making them sympatric. The Guatemalan beaded lizard ("H. charlesbogerti") is the only allopatric one, separated from the nearest population ("H. alvarezi") by 250 km of unsuitable habitat. The Guatemalan beaded lizard is the most endangered of the species, if not of all lizards; it is found only in the dry valley of the Río Motagua in northeastern Guatemala; less than 200 are believed to exist in the wild. The beaded lizard is a specialized vertebrate nest predator, feeding primarily on bird and reptile eggs. A semi-arboreal species, it is found climbing deciduous trees in search of prey