The Gila monster is a species of venomous lizard native to the Southwestern United States and the northwestern Mexican state of Sonora. It is a heavy, slow-moving reptile, up to 56 centimetres (22 in) long, and it is the only venomous lizard native to the United States. Its venomous close relatives, the four beaded lizards inhabit Mexico and Guatemala. The Gila monster is sluggish in nature, so it is not generally dangerous and very rarely poses a real threat to humans. However, it has a fearsome reputation and is sometimes killed despite the species being protected by state law in Arizona.
Gila monster
Evolutionary splitting of the genus Heloderma into species (Reiserer et al) Explanation of the numbers 1 Late Eocene (about 35 million years) 2 Late Miocene (about 10 million years) 3 Pliocene (about 4.4 million years) 4 Pliocene (about 3.0 million years)
The first drawing of a Gila monster by Baird, S. F. (1857)
The dorsal skin of a Gila monster
Lizard is the common name used for all squamate reptiles other than snakes, encompassing over 7,000 species, ranging across all continents except Antarctica, as well as most oceanic island chains. The grouping is paraphyletic as some lizards are more closely related to snakes than they are to other lizards. Lizards range in size from chameleons and geckos a few centimeters long to the 3-meter-long Komodo dragon.
Lizard
A young Mediterranean house gecko in the process of moulting.
Red tegu (Tupinambis rufescens) skull, showing teeth of differing types
Adhesive pads enable geckos to climb vertically.