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 is used to store fat so it can survive during months of estivation. Unlike many other lizards, this tail does not autotomize and cannot grow back if broken. The beaded lizard has a forked, pink tongue which it uses to smell, with the help of a Jacobson's organ; it sticks its tongue out to gather scents and touches it to the opening of the organ when the tongue is retracted. Beaded lizards are found in the Pacific drainages from southern Sonora to southwestern Guatemala and two Atlantic drainages, from central Chiapas to southeastern Guatemala. Their habitats are primarily in the