- Geomyoidea
Taxobox
name = Geomyoid rodents
fossil_range = EarlyEocene - Recent
image_width = 250px
image_caption =Kangaroo rat
regnum =Animal ia
phylum =Chordata
classis =Mammal ia
ordo =Rodent ia
subordo =Castorimorpha
superfamilia = Geomyoidea
superfamilia_authority = Bonaparte, 1845
subdivision_ranks = Families
subdivision = †Eomyidae
†Heliscomyidae
†Florentiamyidae Geomyidae Heteromyidae Geomyoidea is a superfamily of
rodent that contains the pocket gophers (Geomyidae ), the kangaroo rats and mice (Heteromyidae ), and theirfossil relatives.Characteristics
Although dissimilar in overall appearance, gophers have been united with kangaroo rats into a common superfamily for a considerable period of 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 theskull 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 throughoutLaurasia .Relation to other rodents
Geomyoids have been considered to be either
sciuromorphous ormyomorphous depending on the authority. Themasseter muscle does not pass through the infraorbital canal; it cannot due to the position of the canal. Some authorities consider the geomyoids related tosquirrel s,beaver s, andmountain beaver 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, jerboas, and perhaps dormice.
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
**FamilyGeomyidae - pocket gophers
**FamilyHeteromyidae - kangaroo rats and mice, pocket miceCladogram showing interrelationships among geomyoid families following Korth et al. (1991):
Clade | style=font-size:100%;line-height:100%
label1=Geomyoidea
1=Clade
1=†Eomyidae
2=Clade
1=†Heliscomyidae
2=Clade
1=†Florentiamyidae
2=Clade
1=Geomyidae (pocket gophers)
2=Heteromyidae (kangaroo rats and mice, pocket mice)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. ISBN 0-231-11013-8
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