Heloderma

Heloderma, the only genus of the family Helodermatidae, consists of venomous lizards native to the southwestern United States, Mexico and as far south as Guatemala. It includes two separate species, with six subspecies.

Helodermatids (or beaded lizards) are large, stocky, slow-moving reptiles that prefer semi-arid habitats. The tails are short and used as fat storage organs. They are covered with small, non-overlapping bead-like scales, with osteoderms on the underside of the body. Both species are dark in color, with yellowish or pinkish markings.

Uniquely among lizards, members of the family are venomous. Unlike snakes, venom glands are located in the lower jaw, and cannot be ejected under pressure. The venom is typically used only in defense, rather than in subduing prey, and the lizard must chew on its victim to work the venom into the flesh. Venom glands are believed to have evolved early in the lineage leading to the modern helodermatids, as there are indications of their presence even in the 65-million-year-old fossil genus Paraderma.

Helodermatids are carnivorous, preying on rodents and other small mammals, and eating the eggs of birds and reptiles. They are oviparous, laying large clutches of eggs.

Taxonomy

Family Helodermatidae

• Genus Heloderma
• Heloderma horridum, Beaded Lizard
• Heloderma horridum horridum (Wiegmann, 1829)
• Heloderma horridum alvarezi (Bogert & Martên del Campo, 1956)
• Heloderma horridum exasperatum (Bogert & Martên Del Campo, 1956)
• Heloderma horridum charlesbogerti (Campbell & Vannini, 1988)
• Heloderma suspectum, Gila monster
• Heloderma suspectum cinctum (Bogert & Martên Del Campo, 1956)
• Heloderma suspectum suspectum (Cope, 1869)

In captivity

H. h. horridum, H. h. exasperatum, and both subspecies of H. suspectum are frequently found in captivity, and are well represented in zoos throughout much of the world. They are often captive bred for the exotic animal trade, and can command high prices. The other two subspecies of H. horridum are extremely rare, and only a few captive specimens are known.

Notes

External links

• About Beaded Lizards
• Heloderma information
• Family Helodermatidae (Gila Monsters)