Evolution and Classification of the Pocket Gophers of the Subfamily Geomyinae Part 7

*_Geomys quinni_ McGrew, 1944. Geol. Ser., Field Mus. Nat. Hist., 9 (546):49, January 20. Type from Sand Draw local fauna (late Pliocene), Brown County, Nebraska; also known from Broadwater-Lisco local faunas (early Pleistocene), Morrill and Garden counties, Nebraska, Deer Park local fauna (early Pleistocene), Meade County, Kansas.

*_Geomys paenebursarius_ Strain, 1966. Bull. Texas Memorial Mus., 10:36. Type from Hudspeth local fauna (early Pleistocene), Hudspeth County, Texas.

*_Geomys tobinensis_ Hibbard, 1944. Bull. Geol. Soc. Amer., 55:736. Type from Tobin local fauna (middle Pleistocene), Russell County, Kansas; also known from Cudahy local fauna (middle Pleistocene), Meade County, Kansas.

*_Geomys garbanii_ White and Downs, 1961. Contrib. Sci., Los Angeles Co. Mus., 42:1-34, June 30. Type from Vallecito Creek local fauna (middle Pleistocene), San Diego County, California.

*_Geomys bisulcatus_ Marsh, 1871. Amer. Jour. Sci., 3:121. Type from Loup River fossil beds, near Camp Thomas, Nebraska (probably late Pleistocene).

_bursarius_ species-group

*_Geomys parvidens_ Brown, 1908. Mem. Amer. Mus. Nat. Hist., 9:194. (An extinct subspecies of _Geomys bursarius_ according to White and Downs, 1961:6). Type from Conard Fissure local fauna (late Pleistocene), northern Arkansas.

_Geomys bursarius_ (Shaw, 1800). Trans. Linn. Soc. London, 5:227.

Type from somewhere in Upper Mississippi Valley, North America.

_Geomys arenarius_ Merriam, 1895. N. Amer. Fauna, 8:139, January 31.

Type from El Paso, El Paso County, Texas.

_Geomys personatus_ True, 1889. Proc. U. S. Nat. Mus., 11:159, January 5. Type from Padre Island, Cameron County, Texas.

_pinetis_ species-group

_Geomys pinetis_ Rafinesque, 1806. Amer. Monthly Mag., 2 (1):45, November. Type locality restricted to Screven County, Georgia.

_Geomys colonus_ Bangs, 1898. Proc. Boston Soc. Nat. Hist., 28:178, March. Type from Arnot Plantation, about 4 mi. W St. Marys, Camden County, Georgia.

_Geomys c.u.mberlandius_ Bangs, 1898. Proc. Boston Soc. Nat. Hist., 28:180, March. Type from Stafford Place, c.u.mberland Island, Camden County, Georgia.

_Geomys fontanelus_ Sherman, 1940. Jour. Mamm., 21:341, August 13.

Type from 7 mi. NW Savannah, Chatham County, Georgia.

Genus =Orthogeomys= Merriam

1895. _Orthogeomys_ Merriam, N. Amer. Fauna 8:172, January 31.

1895. _Heterogeomys_ Merriam, N. Amer. Fauna 8:179, January 31 (type, _Geomys hispidus_ Le Conte, 1862).

1895. _Macrogeomys_ Merriam, N. Amer. Fauna 8:185, January 31 (type, _Geomys heterodus_ Peters, 1865).

_Type._--_Geomys scalops_ Thomas, 1894, from Tehuantepec, Oaxaca, Mexico.

_Chronologic range._--Late Pleistocene Wisconsin deposits (San Josecito Cave local fauna, Nuevo Leon, Mexico) to Recent.

_Description and discussion._--Species of this genus are of medium to large size. The skull is strongly dolichocephalic in most species; the posterior part of the skull is especially narrow. The angular processes are remarkably short, especially in relation to the length of the mandible. The nasals and rostrum are relatively broad and heavy. The pelage is coa.r.s.e, and often hispid. In some species the hairs are so spa.r.s.ely distributed that the body appears almost naked, and none has so dense a covering of hair as do other genera. The genus occurs entirely within the tropical life-zones, and most of the external features seem to be a.s.sociated with adaptation to tropical conditions.

The upper incisor is unisulcate; the sulcus is usually near the inner border of the tooth, but in some species (subgenus _Orthogeomys_) it is more medial, and in a few individuals with an extremely wide groove the outer lip of the sulcus may actually reach the middle of the tooth. The groove is compressed or open. The premolar is a double column united at the mid-point. The two prisms are of approximately equal size, and the lateral re-entrant folds are so compressed that their sides are parallel. Enamel plates cover the anterior surface and border the re-entrant angles in both upper and lower premolars. As in other members of the tribe, the lower premolar has a fourth enamel plate on the posterior surface of the posterior lophid. In the upper premolar, the enamel plate is reduced to a narrow blade on the lingual side of the loph as in the living species of the genus _Zygogeomys_.

In the subgenus _Orthogeomys_ the posterior plate is usually absent, and otherwise is narrow and near the lingual border of the tooth.

Each lower molar, in the final stage of wear, consists of a single elliptical column having an enamel plate only on the posterior surface. The first and second upper molars are single elliptical columns having one enamel plate on the anterior surface and another on the posterior surface. The plates are separated by a tract of dentine on each side of the tooth. The third upper molar is partly bilophodont, and the two lophs are separated by a deep outer re-entrant fold. In many of the species an inner re-entrant fold also is retained, but in the adult tooth it is less distinct than the outer. In all of the species the posterior loph is long and forms a conspicuous heel; consequently the crown is significantly longer then wide. Moreover, the posterior loph has an enamel plate on each side.

The l.a.b.i.al plate always borders the outer re-entrant fold, and in the subgenus _Orthogeomys_ is infrequently separated into two small plates.

The mandible is relatively long. Its ma.s.seteric ridge is well developed and ma.s.sive. The basitemporal fossa is usually deep and well defined; it tends to be shallow in the subgenus _Orthogeomys_, and in young individuals is hardly more than a slight depression.

Key to the Subgenera of _Orthogeomys_

A Frontal wide and greatly inflated; no interorbital constriction; enamel plate on posterior wall of P4 usually absent, although sometimes having small plate, restricted to lingual end of wall. Subgenus _Orthogeomys_ p. 529

A' Frontal narrow and not greatly inflated; interorbital region decidedly constricted; enamel plate on posterior wall of P4 always present but short and restricted to lingual end of wall.

B Anterior margin of mesopterygoid fossa even with plane of posterior wall of M3; pos...o...b..tal bar weakly developed; anteroposterior occlusal length of M3 equal to, or less than, combined length of M1 and M2.

Subgenus _Heterogeomys_ p. 530

B' Anterior margin of mesopterygoid fossa decidedly behind plane of posterior wall of M3; pos...o...b..tal bar strongly developed; anteroposterior occlusal length of M3 more than combined length of M1 and M2.

Subgenus _Macrogeomys_ p. 531

Subgenus =Orthogeomys= Merriam

1895. _Orthogeomys_ Merriam, N. Amer. Fauna, 8:172, January 31.

_Type._--_Geomys scalops_ Thomas, 1894, from Tehuantepec, Oaxaca, Mexico.

_Chronologic range._--Known only from the Recent.

_Description._--Skull elongated and narrow (many skulls of nearly uniform breadth throughout), being extreme in dolichocephalic specializations; mandibles long and narrow, rami not spreading laterally, being more nearly parallel-sided than in other subgenera; angular processes short; breadth across zygomata not significantly exceeding breadth across mastoid processes (in many skulls considerably less); interorbital area remarkably broad, lacking deep constriction; frontals between orbits greatly inflated laterally, pos...o...b..tal prominence inconspicuous; mesopterygoid fossa extending to level of posterior margin of M3; I having sulcus broader than in other subgenera, mostly on inner half of anterior surface but sometimes overlapping mid-line; enamel plate lacking from posterior wall of P4, rarely retaining narrow vestige near lingual border of posterior loph; M3 having distinct heel, bicolumnar pattern with inner re-entrant fold usually minute, occlusal length less than in other subgenera, length less than combined lengths of M1-2; hair generally coa.r.s.e, sometimes hispid, spa.r.s.e, in lowland forms, so spa.r.s.e as to impart appearance of nakedness.

_Referred species and subspecies._--Fourteen taxa:

_Orthogeomys grandis alleni_ Nelson and Goldman, 1930. Jour. Mamm., 11:156, May 9. Type from near Acapulco, 2000 ft., Guerrero.

_Orthogeomys grandis annexus_ Nelson and Goldman, 1933. Proc. Biol.

Soc. Was.h.i.+ngton, 46:195, October 26. Type from Tuxtla Gutierrez, 2600 ft., Chiapas.

_Orthogeomys grandis carbo_ Goodwin, 1956. Amer. Mus. Novit., 1757:5, March 8. Type from Excurano, 2500 ft., Cerro de San Pedro, 20 km. W Mixtequilla, Oaxaca.

_Orthogeomys grandis felipensis_ Nelson and Goldman, 1930. Jour.

Mamm., 11:157, May 9. Type from Cerro San Felipe, 10 mi. N Oaxaca, Oaxaca.

_Orthogeomys grandis huixtlae_ Villa, 1944. a.n.a.l. Inst. Biol. Univ.

Nac. Mexico, 15:319. Type from Finca Lubeca, 12 km. NE Huixtla, 850 m., Chiapas.

_Orthogeomys grandis grandis_ (Thomas, 1893). Ann. Mag. Nat. Hist., ser. 6, 12:270, October. Type from Duenas, Guatemala.