helodermatid

Helodermatidae, commonly called helodermatids, are a small family of venomous lizards native to the southwestern United States, parts of Mexico, and Central America. The family contains two living species in the genus Heloderma: the Gila monster (Heloderma suspectum) and the Mexican beaded lizard (Heloderma horridum). Heloderms are stout-bodied lizards with bead-like osteodermal scales and stocky limbs. They are among the few lizards known to produce venom; venom glands are located in the lower jaw, and venom is delivered by grooved teeth in the maxilla. Their bites can cause intense pain and swelling and may require medical treatment, though fatalities are rare with modern care.

Habitat and behavior: Helodermatids inhabit arid and semi-arid regions such as deserts, scrublands, and rocky areas. They are primarily carnivorous, feeding on eggs, birds, mammals, lizards, and insects; they are slow-moving and spend much time in burrows or under cover. Reproduction is oviparous; females lay eggs in sheltered sites, with incubation lasting several months.

Evolution and taxonomy: The helodermatids represent a primitive lineage of venomous lizards, with the two living species showing distinct geographic ranges. The group has been the subject of studies on venom evolution and reptile defense. Within Heloderma, the two species are the Gila monster and the Mexican beaded lizard, which together form the extant representatives of the family.