Gila Monster :

Gila Monster, common name for a large and poisonous lizard, one of only two poisonous lizards in the world. It is found in desert areas of Arizona, Nevada, Utah, and New Mexico, especially around the Gila River. The Gila monster is heavily built and moves slowly on four short legs, dragging a thick, short, blunt tail. Fat is stored in the tail, and the lizard can live for months on this reserve. The adult lizard is between 46 and 61 cm (18 and 24 in) in length, often with a strikingly coloured body—black with numerous beads, or tubercles, of pink, orange, yellow, or white; the black head is marbled with pink. The tongue is forked, broad, and flat.
Gila monsters eat small rodents, ants, and the eggs of other desert reptiles. In captivity they have shown a fondness for the eggs of snakes and other lizard species. Gila monster eggs are tough-shelled and about the size of hen eggs. Females lay about a dozen in a wide hole in moist sand, cover them, and then abandon them. The young hatch in a month from the eggs that survive.

Gila monsters bite and then hang on strongly, rolling over on their backs to allow the poison to flow down into the wound and chewing to inflict further punctures. The poison, used mainly as a defence, is secreted by glands in the lower jaw and flows out along grooves on the teeth. The venom attacks the nerve centres controlling the heart, and the bite can be a threat to human beings. The only other poisonous lizard is the beaded lizard, a closely related species found in Mexico and other parts of Central America.
Scientific classification: The Gila monster belongs to the family Helodermatidae. It is classified as Heloderma suspectum.