The Gila Monster (Heloderma suspectum), a poisonous lizard, whose bite is injurious but rarely, if ever, fatal to man, also occurs in the desert regions.
Xenosaurus seems to be an offshoot intermediate between the Iguanidae and the Anguidae; a degraded form of latter is perhaps Aniella of California, whilst Heloderma and Lanthanotus are also specialized and isolated offshoots.
Helodermatidae, with Heloderma of Arizona and Mexico, and Lanthanotus of Borneo.
- The teeth of Heloderma are recurved, with slightly swollen bases, loosely attached to the inner edge of the jaws; each tooth is grooved, and those of the lower jaw are in close vicinity of the series of labial glands which secrete a poison; the only instance among lizards.'
Lanthanotus corneensis, of which only a few specimens are known, is apparently closely allied to Heloderma, although the teeth are not grooved, osteoderms are absent and probably also the poison glands.
Among the venomous reptiles and insects are the rattlesnake, the Gila monster (Heloderma suspectum), a poisonous lizard, and the tarantula (Mygale Heintzii), which, however, are common only in certain places and at certain seasons.