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), 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 infraorbital canal of geomyoids has moved to the side of the snout. 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. Fossil taxa are known from throughout Laurasia.

Relation to other rodents

Geomyoids have been considered to be either sciuromorphous or myomorphous 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 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 beavers 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, 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'' **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 Mammal superfamilies Taxa named by Charles Lucien Bonaparte