''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 ...
of
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
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 ...
s.
References
Anguids
Oligocene reptiles of North America
Oligocene lepidosaurs
Fossil taxa described in 1903
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