REPTILIA: SQUAMATA: HELODERMATIDAE: Heloderma

Heloderma horridum Wiegmann, 1829

Mexican beaded lizard

By Dr. Robert Sprackland. At right, the northern subspecies, Heloderma horridum horridum, photo by author.

Range: Western Mexico in the Sierras, south to Guatemala; absent from Baja.

Diagnosis: A large stubby lizard with beaded skin, a blunt, squarish head with no light markings, and a tail that is banded and longer than the snout-vent length.

Description:

Natural History: Though similar to the Gila monster in form, beaded lizards prefer forested habitats in the mountain foothills. They look awkward, but are good climbers and can swim reasonably well.

Reproduction: Females lay a clutch of large oblong eggs.

Taxonomy & Relationships: Beaded lizards are closely related to the Gila monsters of Arizona and adjacent areas, and together represent the only living members of the Platynota outside the Old World. Fossils of this genus are known from western North America and western Europe.

Variation:

The black beaded lizard, Heloderma horridum alvarezi from southern Mexico. 
This taxon has no light markings. Photo by Robert Applegate.

Additional Comments: Though there are few reliable records of human fatalities from bites from beaded lizards, this species is venomous and a bite should be treated by a professional physician.

Type Specimen:

Literature:

Bogert, Charles and Rafael Martin Del Campo. 1956. The Gila monster and its allies. Bulletin of the American Museum f Natural History 109:1-238. Reprinted and updated 1993 by the Society for the Study of Amphibians and Reptiles.

Campbell, Jonathan and William Lamar. 2004. The venomous reptiles of Western Hemisphere. Two volumes. Comstock Cornell University Press.

Campbell, Jonathan and William Lamar. 1989. The venomous reptiles of Latin America. Comstock Cornell University Press. ISBN:0-8014-2059-8. 

Sprackland, Robert. 1992 Giant Lizards. TFH Publications, Neptune, NJ.