Mexican beaded lizards are large venomous reptiles. Both males and females are stocky with broad heads, although the males' tend to be broader. The scales of these lizards are small, beadlike, and not overlapping. Except for the underside, the majority of their scales are underlaid with bony osteoderms. The base color of Mexican beaded lizards is black and marked with varying amounts of yellow spots or bands, with some individuals being all black in color. They have a short tail that is used to store fat so they can survive during months of estivation. Unlike many other lizards, this tail does not autotomize and cannot grow back if broken. Beaded lizards have a forked, pink tongue which they use to smell, with the help of a Jacobson's organ; they stick their tongue out to gather scents and touche it to the opening of the organ when the tongue is retracted.
Mexican beaded lizards are found in Mexico and southern Guatemala. They occur in the Pacific drainages from southern Sonora to southwestern Guatemala and two Atlantic drainages, from central Chiapas to southeastern Guatemala. These lizards live in tropical deciduous forests, thorn scrub forests, pine-oak forests and in tropical scrubland.
Mexican beaded lizards are only active from April to mid-November, spending about an hour per day above the ground. They are semi-arboreal reptiles that climb trees at night in search of prey. During the day, they hide in burrows or under rocks. Mexican beaded lizards use their venom to kill their prey, and also to weaken potential predators. When threatened, they will also produce hisses.
The mating season of Mexican beaded lizards occurs between September and October. During this time males engage in ritual combat that often lasts several hours; the victor mates with the female. Females lay clutches of 2 to 30 eggs between October and December. The incubation takes around 6-7 months. Young lizards are seldom seen. They are believed to spend much of their early lives underground, emerging at two to three years of age after gaining considerable size. They become reproductively mature at six to eight years of age.
Mexican beaded lizards are surrounded by myth and superstition in much of their native range. They are incorrectly believed, for example, to be more venomous than rattlesnakes or can cause lightning strikes with their tail. As a result of this superstition, locals often kill beaded lizards on sight. These seldom-seen lizards are also poached and sold into the illegal exotic animal trade. They do not reproduce well in captivity, and their scarcity means a high price for collectors. Threatened throughout its range by overcollection and habitat loss for agricultural purposes, the subspecies Guatemalan beaded lizard now is one of the rarest lizards in the world.
According to the IUCN Red List, the total population size of the Mexican beaded lizard is unknown. However, there is an estimated population of the Guatemalan subspecies (Guatemalan beaded lizard) consisting of around 350 mature individuals. Currently, this species is classified as Least Concern (LC) on the IUCN Red List but its numbers today are decreasing.