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 Mandible, lower jaws. About 40% of all mammal specie ...

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

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 Biogeography is the study of the species distribution, distribution of species and ecosystems in geography, geographic space and through evolutionary history of life, geological time. Organisms and biological community (ecology), communities o ...

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 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 (anatomy), rostrum, beak or proboscis. The wet furless surface around the nostrils of the n ...

. 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, or cranium, is typically a bony enclosure around the brain of a vertebrate. In some fish, and amphibians, the skull is of cartilage. The skull is at the head end of the vertebrate. In the human, the skull comprises two prominent ...

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 land ...

. 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 Pa ...

Relation to other rodents

Geomyoids have been considered to be either

sciuromorphous The zygomasseteric system (or zygomasseteric structure) refers to the anatomical arrangement of the masseter muscle and the zygomatic arch (cheek bone) in the skulls of rodents. This system plays a crucial role in the diverse chewing mechanics ...

myomorphous The zygomasseteric system (or zygomasseteric structure) refers to the anatomical arrangement of the masseter muscle and the zygomatic arch (cheek bone) in the skulls of rodents. This system plays a crucial role in the diverse chewing mechanics ...

depending on the authority. The masseter muscle does not pass through the infraorbital canal; it cannot due to the position of the canal. Some authorities consider the geomyoids related to

squirrel Squirrels are members of the family Sciuridae (), a family that includes small or medium-sized rodents. The squirrel family includes tree squirrels, ground squirrels (including chipmunks and prairie dogs, among others), and flying squirrel ...

beaver Beavers (genus ''Castor'') are large, semiaquatic rodents of the Northern Hemisphere. There are two existing species: the North American beaver (''Castor canadensis'') and the Eurasian beaver (''C. fiber''). Beavers are the second-large ...

s, and

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

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 (biology), 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 ...

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" (which is also used for a genus of shield-bugs). †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 †'' Caribeomys incertae sedis'' **Genus †'' Griphomys'' ''

incertae sedis or is a term used for a taxonomy (biology), 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, uncertainty ...

'' **Genus †'' Meliakrouniomys'' ''incertae sedis'' **Family † Eomyidae **Family † Heliscomyidae **Family † Florentiamyidae **Family Geomyidae - pocket gophers **Family Heteromyidae - 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 Castorimorpha Mammal superfamilies Taxa named by Charles Lucien Bonaparte