Gila Monster is a name commonly given to the poisonous lizard Heloderma suspectum, also called Sonoran Heloderm. It is one of the largest lizards of North America, and is found in the sandy deserts of New Mexico, Arizona, and Texas. Its scales are brilliant orange and jet black. Its poisonous qualities it shares with its congener the Heloderma horridum of Mexico, which, like snakes, has grooved teeth and highly developed salivary glands at their bases. Its bite is rapidly fatal to small mammals and birds, and very injurious, though seldom fatal, to man. The heloderms are the only lizards ascertained to be venomous.