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Geoffrey R. Smith, PhD

Gila monsters and Mexican beaded lizards


Class Reptilia Order Squamata Suborder Scleroglossa Family Helodermatidae

Large, stout, venomous lizards with distinctive, beadlike scales (osteoderms) on the dorsal surfaces of head, limbs, body, and tail


12-18 in (30-45 cm) snout-to-vent length; 14-39 in (35-100 cm) total length; 1.0-4.4 lb (450g-2 kg)

Number of genera, species

1 genus; 2 species

Hot desert, tropical deciduous forest

Conservation status

Vulnerable: 2 species



Desert regions of the southwestern United States and northwestern Mexico; Pacific drainages along the western slope of Mexico and southern Guatemala; and two Atlantic drainages in Chiapas and eastern Guatemala

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