Helodermatidae

Helodermatidae; Temporal range: ; Eocene - Holocene, 37–0 Ma PreꞒ Ꞓ O S D C P T J K Pg N
	Gila Monster (Heloderma suspectum)
	Mexican beaded lizard (Heloderma horridum)
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Order:	Squamata
Clade:	Monstersauria
Family:	Helodermatidae; Gray, 1837
Genera
	Heloderma; †Eurheloderma; †Lowesaurus;

The Helodermatidae or beaded lizards are a small family of lizards endemic to North America today, mainly found in the Isthmus of Tehuantepec in Oaxaca, the central lowlands of Chiapas, on the border of Guatemala, and in the Nentón River Valley.^[1] But they were 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.^[2]

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 Eurheloderma gallicum from Europe (France).^[3]

References

^ Gómez-Cruz, A.; Hernández, N. G; Ruiz-Castillejos, C.; Espinoza-Medinilla, E. E.; De Fuentes-Vicente, J. A. (2021). "Effect of climate change on the potential distribution of Heloderma alvarezi (Squamata, Helodermatidae)". ZooKeys (1070): 1–12. doi:10.3897/zookeys.1070.69186. PMC 8599303. PMID 34819767.
^ 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.
^ 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.

[1] Gómez-Cruz, A.; Hernández, N. G; Ruiz-Castillejos, C.; Espinoza-Medinilla, E. E.; De Fuentes-Vicente, J. A. (2021). "Effect of climate change on the potential distribution of Heloderma alvarezi (Squamata, Helodermatidae)". ZooKeys (1070): 1–12. doi:10.3897/zookeys.1070.69186. PMC 8599303. PMID 34819767.

[2] 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.

[3] 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.

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