Geomyoidea is a superfamily of

rodent Rodents (from Latin , 'to gnaw') are mammals of the Order (biology), order Rodentia (), which are characterized by a single pair of continuously growing incisors in each of the upper and lower jaws. About 40% of all mammal species are roden ...

that contains the pocket gophers ( Geomyidae), the kangaroo rats and mice (

Heteromyidae Heteromyidae is a family of rodents consisting of kangaroo rats, kangaroo mice, pocket mice and spiny pocket mice. Most heteromyids live in complex burrows within the deserts and grasslands of western North America, though species within the ...

), and their

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

relatives.

Characteristics

Although dissimilar in overall appearance, gophers have been united with kangaroo rats into a common superfamily for a considerable time. The superfamily Geomyoidea is among the few superfamilial relationships in rodents that is not subject to much controversy. Overall morphology, the fossil record, molecular analyses, and biogeography all support this relationship. Geomyoids are most noticeably characterized by the position of the infraorbital canal. Unlike all other rodents who have the opening of the infraorbital canal facing forward, geomyoids have an infraorbital canal that faces to the side. Instead of passing through the

zygoma The term zygoma generally refers to the zygomatic bone, a bone of the human skull commonly referred to as the cheekbone or malar bone, but it may also refer to: * The zygomatic arch, a structure in the human skull formed primarily by parts of the z ...

, the infraorbital canal of geomyoids has moved to the side of the

snout A snout is the protruding portion of an animal's face, consisting of its nose, mouth, and jaw. In many animals, the structure is called a muzzle, rostrum, or proboscis. The wet furless surface around the nostrils of the nose of many mammals is ...

. This condition is so pronounced and the snout so narrow in heteromyids that the infraorbital canals from either side connect. Essentially, if the

skull The skull is a bone protective cavity for the brain. The skull is composed of four types of bone i.e., cranial bones, facial bones, ear ossicles and hyoid bone. However two parts are more prominent: the cranium and the mandible. In humans, t ...

of a heteromyid is viewed from the side, the viewer can see directly through it. Modern geomyoids are mostly restricted to North America, but some representatives have extended their range into South America since the

Great American Interchange The Great American Biotic Interchange (commonly abbreviated as GABI), also known as the Great American Interchange and the Great American Faunal Interchange, was an important late Cenozoic paleozoogeographic biotic interchange event in which la ...

. Fossil taxa are known from throughout

Laurasia Laurasia () was the more northern of two large landmasses that formed part of the Pangaea supercontinent from around ( Mya), the other being Gondwana. It separated from Gondwana (beginning in the late Triassic period) during the breakup of Pan ...

Relation to other rodents

Geomyoids have been considered to be either sciuromorphous or myomorphous depending on the authority. The

masseter muscle In human anatomy, the masseter is one of the muscles of mastication. Found only in mammals, it is particularly powerful in herbivores to facilitate chewing of plant matter. The most obvious muscle of mastication is the masseter muscle, since it ...

does not pass through the infraorbital canal; it cannot due to the position of the canal. Some authorities consider the geomyoids related to squirrels,

beaver Beavers are large, semiaquatic rodents in the genus ''Castor'' native to the temperate Northern Hemisphere. There are two extant species: the North American beaver (''Castor canadensis'') and the Eurasian beaver (''C. fiber''). Beavers a ...

s, and

mountain beaver The mountain beaver (''Aplodontia rufa'')Other names include mountain boomer, ground bear, giant mole, gehalis, lesser sasquatch, sewellel, suwellel, showhurll, showtl, and showte, as well as a number of Chinookan and other Native American terms ...

s on this basis. The masseter muscle does attach directly behind the zygomatic arch in a manner very different from sciuromorphs. Some authorities consider geomyoids myomorphs based on this feature. This suggests they may be related to

mice A mouse ( : mice) is a small rodent. Characteristically, mice are known to have a pointed snout, small rounded ears, a body-length scaly tail, and a high breeding rate. The best known mouse species is the common house mouse (''Mus musculus' ...

, jerboas, and perhaps

dormice A dormouse is a rodent of the family Gliridae (this family is also variously called Myoxidae or Muscardinidae by different taxonomists). Dormice are nocturnal animals found in Africa, Asia, and Europe. They are named for their long, dormant hi ...

Taxonomy

The family †Eomyidae is alternatively referred to as a member of the superfamily Geomyoidea or as a separate superfamily (†Eomyoidea) within the shared infraorder Geomorpha. †Florentiamyidae and †Heliscomyidae are usually placed within the superfamily Geomyoidea regardless of if eomyids are treated as a separate superfamily or not (Korth ''et al.'', 1991). McKenna and Bell (1997) do not recognize heliscomyids as a distinct family, placing the one or two heliscomyid genera in Geomyoidea ''incertae sedis''. Sometimes the pocket gophers and heteromyids are placed as separate subfamilies within a single family (Geomyidae). These subfamilies are Geomyinae and Heteromyinae respectively. *Superfamily Geomyoidea **Genus †'' Griphomys'' ''

incertae sedis ' () or ''problematica'' is a term used for a taxonomic group where its broader relationships are unknown or undefined. Alternatively, such groups are frequently referred to as "enigmatic taxa". In the system of open nomenclature, uncertain ...

'' **Genus †'' Meliakrouniomys'' ''incertae sedis'' **Family † Eomyidae **Family † Heliscomyidae **Family † Florentiamyidae **Family Geomyidae - pocket gophers **Family

- kangaroo rats and mice, pocket mice Cladogram showing interrelationships among geomyoid families following Korth ''et al.'' (1991):

References

*Korth, W.W., J.H. Wahlert, and R.J. Emry, 1991. A new species of ''Heliscomys'' and recognition of the family Heliscomyidae (Geomyoidea: Rodentia) ''Journal of Vertebrate Paleontology'' 11(2):247-256. *McKenna, Malcolm C., and Bell, Susan K. 1997. ''Classification of Mammals Above the Species Level.'' Columbia University Press, New York, 631 pp. {{Taxonbar, from=Q1757560 Mammal superfamilies Taxa named by Charles Lucien Bonaparte