Mexican beaded lizard generic name "Heloderma" means "studded skin", from the Ancient Greek words "hêlos" (ἧλος)—the head of a nail or stud—and "dérma" (δέρμα), meaning skin. Its specific name, "horrĭdum", is the Latin word meaning rough or rude. The four subspecies of beaded lizard, elevated to full species in 2013, are: Adult beaded lizards range from in length. They are substantially larger than the Gila monster, which only reaches lengths of . The snout-to-vent length of a beaded lizard averages . The average body mass of an adult beaded lizard is , about 45% heavier than the average mass of a gila monster,
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