Heloderma

Heloderma Fossil range: Late Cretaceous to Recent
Gila monster, Heloderma suspectum
Scientific classification
Kingdom: Animalia Phylum: Chordata Class: Sauropsida Order: Squamata Suborder: Scleroglossa Infraorder: Anguimorpha Superfamily: Varanoidea Family: Helodermatidae Genus: Heloderma Wiegmann, 1829
Species
Heloderma horridum Heloderma suspectum

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. Their closest living relatives are the anguid lizards.^[1]

Helodermatids (or beaded lizards) are large, stocky, slow-moving reptiles that prefer semi-arid habitats.^[2] 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.^[3]

Members of the family are venomous.^[4] 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.^[3][5] Venom production among lizards was long thought to be unique to this genus, but may be present in several monitor lizards and agamids as well.^[1] This controversial new view holds that venom production dates back to the common ancestor of the clade Toxicofera, which includes all snakes and 13 families of lizards.^[1]

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.^[3]

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

Sources

Ariano-Sánchez, D. 2008. Envenomation by a wild Guatemalan beaded lizard Heloderma horridum charlesbogerti. Clinical toxicology 46 (9): 897-899. [1]

Ariano-Sánchez, D. & G. Salazar. 2007. Notes on the distribution of the endangered lizard, Heloderma horridum charlesbogerti, in the dry forests of eastern Guatemala: an application of multi-criteria evaluation to conservation. Iguana 14: 152-158. [2]

Ariano-Sánchez, D. 2006. The Guatemalan beaded lizard: endangered inhabitant of a unique ecosystem. Iguana 13: 178-183. [3]

CONVENTION ON INTERNATIONAL TRADE IN ENDANGERED SPECIES OF WILD FAUNA AND FLORA. 2007. Resume of the 14th Convention of the Parts. The Hague. The Netherlands. [http://www.ssn.org/Meetings/cop/cop14/Other/CoP14_results.pdf

Heloderma Project ZOO ATLANTA, IRCF, ZOOTROPIC, project [4]

External links

Wikispecies has information related to: Helodermatidae

• Media related to Helodermatidae at Wikimedia Commons
• About Beaded Lizards
• Heloderma information
• Family Helodermatidae (Gila Monsters)