''Helodermoides'' is an extinct

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

anguid Anguidae refers to a large and diverse family of lizards native to the Northern Hemisphere. Common characteristics of this group include a reduced supratemporal arch, striations on the medial faces of tooth crowns, osteoderms, and a lateral fold ...

lizards from the

Oligocene The Oligocene ( ) is a geologic epoch of the Paleogene Period and extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that define the epoch are well identified but the ...

of North America. The genus is

monotypic In biology, a monotypic taxon is a taxonomic group (taxon) that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies or smaller, infraspecific taxa. In the case of genera, the term "unispec ...

, including only the species ''Helodermoides tuberculatus''. ''Helodermoides'' belongs to an extinct subfamily of anguids called

Glyptosaurinae Glyptosaurinae is an extinct subfamily of anguid lizards that lived in the Northern Hemisphere during the Late Cretaceous and the Paleogene. Description Glyptosaurines are known primarily from their osteoderms, scale-like pieces of bone that ar ...

. In addition to many fragmentary bones, several complete skeletons of ''Helodermoides'' are known. Like other glyptosaurines, ''Helodermoides'' was covered in small scale-like bones called

osteoderm Osteoderms are bony deposits forming scales, plates, or other structures based in the dermis. Osteoderms are found in many groups of extant and extinct reptiles and amphibians, including lizards, crocodilians, frogs, temnospondyls (extinct amp ...

s. The osteoderms covering its skull are hexagonal, tightly interlocking, raised, and rounded. One fossil of ''Helodermoides'' preserves a fused mass of osteoderms at the tip of a shortened tail, thought to represent healing after the end of the tail fell off. The tail would not have been able to grow back because the osteoderms formed a thick bony cap preventing growth. The ability to lose a tail, called

autotomy Autotomy (from the Greek language, Greek ''auto-'', "self-" and ''tome'', "severing", wikt:αὐτοτομία, αὐτοτομία) or self-amputation, is the behaviour whereby an animal sheds or discards one or more of its own appendages, usual ...

, is also present in living

References

Anguids Oligocene reptiles of North America Oligocene lepidosaurs Fossil taxa described in 1903 {{paleo-lizard-stub