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,
Arizona night lizard young of the lizard are born live, usually one or two around August or September. As the lizard tends not to move about and generally avoids humans, not much is known about it. The species grows to maximum size of about 10 cm. The head is covered with large, smooth plates. Body scales are small, while belly scales are rectangular. The dorsal side is covered with many small dark spots tending to form rows. The eyes are large and round with a vertical pupil (similar to a snake's eye). The species is a secretive lizard. It feeds, reproduces, and lives