Introduction 



This bibliography is a compilation of references on the venomous lizards of the family 

 Helodermatidae, the beaded lizard {Heloderma horridum) and Gila monster {Heloderma suspectum). Like 

 all venomous reptiles, the Helodermatidae have long been shrouded in mystery, misinformation, and myth. 

 This mystique is even reflected in their specific epithets: horridum (the horrible one) and suspectum (the 

 suspect). In 1869, E.D. Cope chose the epithet "suspectum" for the Gila monster because he "suspected" it 

 was venomous but it took the scientific community nearly another half century to agree that, indeed this 

 was true. Unlike most other lizards, helodermatids cannot run swiftly. A painful venomous bite is an 

 important feature of their ability to avoid predators. For us humans, the venom of helodermatid lizards is 

 proving to be a surprising source of pharmacologically active peptides, some of which hold great promise 

 for treating disease, such as diabetes. 



Other discoveries within this bibliography reveal that the two remaining species of helodermatid 

 lizards are relicts of a more diverse lineage (the Monstersauria) that includes at least seven other genera 

 (Estesia, Eurheloderma, Gobiderma, Lowesaurus, Palaeosaniwa, Paraderma, and Primaderma) inhabiting 

 arid, temperate, and subtropical regions across Europe, Asia, and North America. The Monstersauria 

 (Helodermatidae) has been traced back nearly 100 million years, and has somehow managed to survive the 

 great Cretaceous extinctions, which vanquished the dinosaurs 65 million years ago. The genus Heloderma 

 has existed since at least the early Miocene (about 23 million years ago) and has undergone relatively little 

 gross morphological change over this time, prompting paleontologists to dub it a living fossil. 



The references in this bibliography also tell a story of sedentary nest predators that return year after 

 year to the same foraging areas and shelters. Males vie for access to females by performing spectacular 

 combat rituals, reminiscent of the entwining combat dances of viperid snakes. Their low metabolic rates, 

 ability to eat large meals, and to store energy as fat in their sausage-shaped tails enable helodermatid lizards 

 to offset the energy costs of searching for a widely distributed food source and to subsist long periods 

 without feeding. These traits make frequent foraging unnecessary and contribute to their ability to feed 

 almost solely on the contents of vertebrate eggs and young in their nests, a specialized feeding niche shown 

 by few other lizards. The ecology, physiology and behavior of the Helodermatidae has helped us refine our 

 thinking about reptilian life in the slow lane, and as ancient members of the clade from which snakes likely 

 arose, they are putting a new spin on what it means to be a lizard. 



Papers in this bibliography are also sounding an early warning. Throughout most of their range, 

 helodermatid lizards inhabit only a fraction of what was once suitable habitat. During the last 150 years, 

 thousands of square miles of desert and tropical dry forest habitats have been cleared for agriculture, 

 residential, and recreational development. Although helodermadd lizards are not in immediate danger of 

 extinction, some populations are in peril, especially along the margins of their geographic range. 

 Heloderma affords us an opportunity for a proactive approach in conserving biodiversity. It will be far 

 more difficult for Heloderma populations to recover, if they can recover at all, if we wait until they are on 

 the endangered species list before we take action to preserve their spectacular habitats. As interest in this 

 fascinating family of lizards continues to grow, so will the list of references included here. We still have 

 much to learn about helodermatid lizards and what lies ahead could be even more interesting than what 

 we've already discovered, but only if we act responsibly to ensure their survival. 



This bibliography provides the essential references for the family Helodermatidae. Both technical 

 and popular articles dealing with new information or synthesis of previous knowledge are included. It was 

 assembled from a variety of sources, including Biological Abstracts, Zoological Record, Synopsis of the 



