Gila Monster

The Gila monster (Heloderma suspectum, /ˈhiːlə/ HEE-lə) is a species of venomous lizard native to the southwestern United States and northwestern Mexican state of Sonora. A heavy, typically slow-moving lizard, up to 60 cm (2.0 ft) long, the Gila monster is the only venomous lizard native to the United States and one of only two known species of venomous lizards in North America, the other being its close relative, the Mexican beaded lizard (H. horridum). Although the Gila monster is venomous, its sluggish nature means it represents little threat to humans. However, it has earned a fearsome reputation, and is sometimes killed despite being protected by state law in Arizona.
== Description ==
In this species, the largest extant lizard native to North America north of the Mexican border (non-natives like green iguanas are larger), snout-to-vent length is from 26 to 36 cm (10 to 14 in). The tail is about 20% of the body size and the largest specimens may reach 51 to 56 cm (20 to 22 in) in total length. Body mass is typically in the range of 350 to 700 g (0.77 to 1.54 lb), with 11 males having been found to average 468 g (1.032 lb). Reportedly, the very heaviest, largest specimens can weigh as much as 2,300 g (5.1 lb).
The Gila monster has one close living relative, the beaded lizard (H. horridum), as well as many extinct relatives in the Helodermatidae, the evolutionary history of which may be traced back to the Cretaceous period. The genus Heloderma has existed since the Miocene, when H. texana lived, and fragments of osteoderms from the Gila monster have been found in late Pleistocene (10,000–8,000 years ago) deposits near Las Vegas, Nevada. Because the helodermatids have remained relatively unchanged morphologically, they are occasionally regarded as living fossils. Although the Gila monster appears closely related to the monitor lizards (varanids) of Africa, Asia and Australia, their wide geographical separation and the unique features not found in the varanids indicate the Gila monster is better placed in a separate family.
The name "Gila" refers to the Gila River Basin in the U.S. states of New Mexico and Arizona, where the Gila monster was once plentiful. Heloderma means "studded skin", from the Ancient Greek words helos (ἧλος), "the head of a nail or stud", and derma (δέρμα), "skin". Suspectum comes from the describer, paleontologist Edward Drinker Cope, who suspected the lizard might be venomous due to the grooves in the teeth.
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