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 with large specimens exceeding . Maximum weight known is Although males are slightly larger than females, the lizards are not sexually dimorphic. Both males and females are stocky with broad heads, although the males' tend to be broader. The beaded lizard's scales are small, beadlike, and not overlapping. Except for the lizard's underside, the majority of its scales are underlaid with bony osteoderms. Their base color is black and marked with varying amounts of yellow spots or bands, with the exception of "H. alvarezi", which tends to be all black in color. The beaded lizard has a short tail which