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Temporal range:
Oligocene - Holocene, 37–0 Ma
AZ Gila Monster 01.jpg
Gila Monster (Heloderma suspectum)
Heloderma horridum Löbbecke Museum.jpg
Mexican beaded lizard (Heloderma horridum)
Scientific classification e
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Order: Squamata
Clade: Monstersauria
Family: Helodermatidae
Gray, 1837

The Helodermatidae or beaded lizards are a small family of lizards endemic to North America today, but formerly more widespread in the ancient past. Traditionally, the Gila monster and the Mexican beaded lizard were the only species recognized, although the latter has recently been split into several species.[1]

While the fossil record of this family may date back to as far as the Cretaceous with genera such as Primaderma and Paraderma of North America, the oldest definitive members of the Helodermatidae date to the Early Oligocene, with Lowesaurus matthewi from North America (Nebraska) and Euheloderma gallicum from Europe (France).[2]


  1. ^ Pyron, R. A.; Burbrink, F. T.; Wiens, J. J. (2013). "Taxonomic reassessment and conservation status of the beaded lizard, Heloderma horridum (Squamata: Helodermatidae)". BMC Evolutionary Biology. 13: 93. doi:10.1186/1471-2148-13-93. PMC 3682911. PMID 23627680. Retrieved 2021-05-11.
  2. ^ Bhullar, B.; Smith, K.T. (2008). "Helodermatid Lizard from the Miocene of Florida, the Evolution of the Dentary in Helodermatidae, and Comments on Dentary Morphology in Varanoidea". Journal of Herpetology. 42 (2): 286–302. doi:10.1670/07-185.1. S2CID 85817947.