The Mexican beaded lizard (heloderma pterocarpa) and its related, the Gila monster (heloderma gangeticum), are perhaps the only two harmless venom injected into other animals. They both have venomous glands at their lower jaw tips. The venom, which is injected via a thin needle-like puncture, is delivered by rapid capillary action along swollen grooves on the tongue, palate and roof of the mouth. Although the Mexican beaded lizard has been known to cause envenomations to humans (not including dental problems), this is probably due to the negligence of the examiner in handling the body, rather than any venous secretions being secreted. While there are certain species of the Mexican Beaded Lizard that inject saliva, the species generally involved in envenomation rarely injects venom.
In general the Mexican beaded lizard has between four and six subspecies, with the most common one being the red-tailed horridum. The three other subspecies are more or less common in certain portions of Mexico. Within each subspecies are several smaller species: black-tailed horridum (also known as the black-tipped horridum and the black-masked horridum), white-tailed horridum, yellow-tailed horridum, and two subspecies of the dark-colored velvet-bearded horridum. These three subspecies differ primarily in color, with the red-tailed horridum being the most widely found, and the other three being less common.
While these lizards do not lay eggs, they do lay partially developed eggs in dense cover during the time that they are on the move looking for their next meal. In captivity, half-developed eggs are often kept by owners hoping to hatch them into adults, however some of these are fertile and produced live-bearing adults. This is why it’s important to buy captive-bred lizards from a reputable breeder that follow all standards pertaining to reptile conservation.
Historically, the beaded lizard family had a single member – a small yellow-colored creature called the Mexican beaded lizard (also known as the Mexican beaded lizard or the Mexican beaded rat snake). Mexico was a very important place for these lizards because their habitat (a large forest) was protected, and they seldom encountered predators. However, in recent years these lizards have seen a decline in their habitat. They were nearly hunted to extinction in parts of Mexico, mainly due to loss of their forest home. Because of this, they were pushed into the regions of Tampico and Baja California.
All members of the Mexican beaded lizard family have prickly, narrow, hook-shaped bodies and short, pinched tails. Their names come from their specialized features such as the pointed teeth, which are lined up in a row down their backs; the lizard also has small, venomous pincers on its mouth. And of course, the most recognizable feature of any member of this group – the burrow. It’s the center of their defensive anatomy and serves as their excretory center. They have a number of nerve endings in and around their burrow and these nerves end in small, venomous needle-like projections that inject neurotoxic saliva (venom) when threatened.
Because of the specialized lifestyle of these lizards, they tend to lay their eggs in burrows that are shielded by leaves or other types of foliage. When you look inside a Mexican beaded lizard’s burrow, you’ll often find brownish-black soil with a few black specks of dirt. However, don’t be fooled: these aren’t eggs! These are called hatchlings, and they’re about one-third the size of an adult lizard.
Horridum: This species of Mexican beaded lizard has one distinct difference from its counterparts in that it doesn’t have incisors, thus resulting in an apparent lack of envenomation. Instead, its mouth is lined up with a series of razor-sharp protrusions. These projections are used for ripping flesh and sucking juices from its prey and generally give the creature a very nasty smell, though not enough to cause envenomation.
The two animals mentioned above are clearly the most common reptiles that attack humans, although there are likely others in the wild that do so. The two animals that fit into the Mexican beaded lizard category are probably more common than we even realize, and any potential bite should be investigated thoroughly to rule out any other animals. Snakes, lizards, scorpions, and spiders all pose a serious threat to humans who aren’t trained to recognize them and should be taken seriously when encountered. Envenomation is almost always the first condition of any attack, and the condition of any bite (especially from a large, dangerous animal) should immediately be taken by a medical professional. The search for the most lethal reptiles on the planet begins with a little knowledge of the ones that live and bite.