restricted to the posterior surface as in _Zygogeomys_, _Orthogeomys_,
and _Pappogeomys_. Paulson (_loc. cit._) found a thin enamel plate on
the anterior surfaces of the lower molars in about five per cent of
the individuals of _Geomys tobinensis_ from the Cudahy local fauna
(middle Pleistocene, deposits of the late Kansan glaciation). An
anterior plate is unknown in other members of the tribe Geomyini,
except in the primitive genus _Pliogeomys_ of the middle Pliocene.
Occurrence of the plate in _Geomys tobinensis_ is an atavistic trait.
Primitive dental patterns occur occasionally in geomyids, as pointed
out above, but the frequency of occurrence in _G. tobinensis_ is
higher than would be expected.
M1 and M2, like the lower molars, are elliptical in cross-section.
Complete enamel plates on the anterior and posterior surfaces are
separated by tracts of dentine on the sides of each tooth. M3 is
usually suborbicular (sometimes subtriangular) in cross-section. The
tooth is not especially elongated posteriorly and usually has no
definite heel; therefore, it is not significantly longer than wide.
Living species of _Geomys_ rarely have a well defined outer re-entrant
fold on M3; less than 10 per cent of the individuals (and usually only
one side in each individual in which it occurs) have it, although a
shallow inconspicuous groove occurs more frequently. The biprismatic
molar characteristic of the ancestral morphotype is less often found
in _Geomys_ than in any other living member of the tribe Geomyini. The
outer re-entrant fold and biprismatic pattern are more often present
in the extinct species _Geomys garbanii_ of the Middle Pleistocene
than in other species. Less than 24 per cent of the third upper molars
in _Geomys garbanii_ lack a tract of the re-entrant fold and more than
38 per cent have a well developed outer fold (see White and Downs,
1961:13, 18). The bicolumnar pattern, although incomplete, would be
clearly evident in those teeth having a well marked re-entrant fold;
the pattern occurs less frequently in those teeth with no fold or only
a slight one. M3 of geomyids is not usually recovered and, therefore,
the occlusal pattern of M3 is unknown in most extinct kinds of
_Geomys_. In Recent _Geomys_ the fold is more common in the eastern
_pinetis_ species-group than in the western _bursarius_ species-group.
The masseteric ridge on the outer side of the mandible is well
developed in all species of the genus. The position of the mental
foramen relative to the anterior part of the ridge varies with
individuals and according to species. The basitemporal fossa is always
present, but is shallower in the late Pliocene and Pleistocene species
than in Recent species. The angular process is short.
_Referred species._--The twelve species, five of which are extinct,
are as follows:
_quinni_ species-group
*_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 cumberlandius_ Bangs, 1898. Proc. Boston Soc. Nat. Hist.,
28:180, March. Type from Stafford Place, Cumberland 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,
México.
_Chronologic range._--Late Pleistocene Wisconsin deposits (San
Josecito Cave local fauna, Nuevo León, México) 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 coarse, and often hispid. In some species the
hairs are so sparsely 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 associated 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 labial 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 masseteric ridge is well
developed and massive. 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; postorbital 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; postorbital 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,
México.
_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,
postorbital 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 coarse, sometimes
hispid, sparse, in lowland forms, so sparse 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. Washington, 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. Anal. Inst. Biol. Univ.
Nac. México, 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 Dueñas, Guatemala.
_Orthogeomys grandis latifrons_ Merriam, 1895. N. Amer. Fauna,
8:178, January 31. Type from Guatemala, exact locality
unknown.
_Orthogeomys grandis nelsoni_ Merriam, 1895. N. Amer. Fauna, 8:176,
January 31. Type from Mt. Zempoaltepec, 8000 ft., Oaxaca.
_Orthogeomys grandis pluto_ Lawrence, 1933. Proc. New England Zool.
Club, 13:66, May 8. Type from Cerro Cantoral, north of
Tegucigalpa, Honduras.
_Orthogeomys grandis scalops_ (Thomas, 1894). Ann. Mag. Nat. Hist.,
ser. 6, 13:437, May. Type from Tehuantepec, Oaxaca.
_Orthogeomys grandis soconuscensis_ Villa, 1949. Anal. Inst. Biol.
Univ. Nac. México, 19:267, April 8. Type from Finca
Experanza, 710 m., 45 km. (by road) NW Huixtla, Chiapas.
_Orthogeomys grandis guerrerensis_ Nelson and Goldman, 1930. Jour.
Mamm., 11:158, May 9. Type from El Limón, in valley of Río de
las Balsas approximately 20 mi. NW La Unión, Guerrero.
_Orthogeomys cuniculus_ Elliot, 1905. Proc. Biol. Soc. Washington,
18:234, December 9. Type from Zanatepec, Oaxaca.
_Orthogeomys pygacanthus_ Dickey, 1928. Proc. Biol. Soc. Washington,
41:9, February 1. Type from Cacaguatique, 3500 ft., Dept. San
Miguel, El Salvador.
Subgenus =Heterogeomys= Merriam
1895. _Heterogeomys_ Merriam, N. Amer. Fauna, 8:179, January 21.
_Type._--_Geomys hispidus_ Le Conte, 1852, from near Jalapa, Veracruz.
_Chronologic range._--Late Pleistocene, Wisconsin deposits (San
Josecito Cave local fauna, Nuevo León) to the Recent.
_Description._--Skull dolichocephalic (less so than in the other
subgenera); zygomata more widely spreading than in _Orthogeomys_;
ramus and angular process short; interorbital area noticeably
constricted; frontals between orbits neither exceptionally broad or
inflated; mesopterygoid fossa extending to level of posterior margin
of M3; I having sulcus on inner third of anterior surface usually
narrower than in subgenus _Orthogeomys_; enamel plate on posterior
wall of P4 restricted to lingual half of loph; M3 distinctly
biprismatic, posterior loph usually circumscribed by shallow inner
re-entrant fold and outer deep fold well developed in all members of
genus; posterior loph forming conspicuous heel longer than in subgenus
_Orthogeomys_; occlusal length equal to or slightly less than combined
lengths of M1-2; hair coarse and hispid but never so sparse as to
impart appearance of nakedness.
_Referred species and subspecies._--Eleven taxa:
*_Orthogeomys onerosus_ (Russell, 1960). Univ. Kansas Publ., Mus.
Nat. Hist., 9 (21):544, January 14. Type from San Josecito Cave
local fauna, Upper Pleistocene, Nuevo León.
_Orthogeomys hispidus cayoensis_ (Burt, 1937). Occ. Papers Mus.
Zool., Univ. Michigan, 365:1, December 16. Type from Mountain
Pine Ridge, 12 mi. S El Cayo, British Honduras.
_Orthogeomys hispidus chiapensis_ (Nelson and Goldman, 1929). Proc.
Bio. Soc. Washington, 42:151, March 30. Type from Tenejapa, 16
mi. NE San Cristobal, Chiapas.
_Orthogeomys hispidus concavas_ (Nelson and Goldman, 1929). Proc.
Biol. Soc. Washington, 42:148, March 30. Type from Pinal de
Amoles, Querétaro.
_Orthogeomys hispidus hispidus_ (Le Conte, 1852). Proc. Acad. Nat.
Sci. Philadelphia, 6:158. Type from near Jalapa, Veracruz.
_Orthogeomys hispidus latirostris_ (Hall and Alvarez, 1961). Anal.
Escuela Nac. Ciencias Biol., 10:121, December 20. Type from
Hacienda Tamiahua, Cabo Rojo, Veracruz.
_Orthogeomys hispidus negatus_ (Goodwin, 1953). Amer. Mus. Novit.,
1620:1, May 4. Type from Gomez Ferias, 1300 ft., about 45 mi. S
Ciudad Victoria, 10 km. W Pan American Highway, Tamaulipas.
_Orthogeomys hispidus tehuantepecus_ (Goldman, 1939). Jour.
Washington Acad. Sci., 29:174, April 15. Type from mountains 12
mi. NW Santo Domingo and about 60 mi. N Tehuantepec, 1600 ft.,
Oaxaca.
_Orthogeomys hispidus torridas_ (Merriam, 1895). N. Amer. Fauna,
8:183, January 31. Type from Chichicaxtle, Veracruz.
_Orthogeomys hispidus yucatanensis_ (Nelson and Goldman, 1929).
Proc. Biol. Soc. Washington, 42:150, March 30. Type from
Campeche, Campeche.
_Orthogeomys lanius_ (Elliot, 1905). Proc. Biol. Soc. Washington,
18:235, December 9. Type from Xuchil, Veracruz.
Subgenus =Macrogeomys= Merriam
1895. _Macrogeomys_ Merriam, N. Amer. Fauna, 8:185, January 31.
_Type._--_Geomys heterodus_ Peters, 1865, from Costa Rica, exact
locality unknown.
_Chronologic range._--Known only from the Recent.
_Description._--Skull dolichocephalic in varying degree (overlapping
subgenera _Orthogeomys_ and _Heterogeomys_ in this respect); mandibles
elongated, not spreading far laterally; angular processes decidedly
short; breadth across zygomata in no instance significantly exceeding
mastoid breadth; interorbital area strongly constricted; frontals
between orbits slightly inflated laterally (especially in forms having
more strongly dolichocephalic skulls); postorbital prominence
conspicuous; anterior margin of mesopterygoid fossa terminating well
behind M3; I having narrow and deep sulcus entirely on inner third of
anterior surface; enamel plate on posterior wall of P4 restricted to
inner half of loph; M3 bilophodont (outer and inner re-entrant folds
each circumscribing a loph), posterior loph remarkably elongated and
forming pronounced heel, length of crown more than combined lengths of
M1-2; hair wooly in some individuals, harsh in others but seldom
hispid, never so sparse as in subgenus _Orthogeomys_; some species
having white markings, especially on lumbar region and head.
_Referred species and subspecies._--Eleven taxa:
_Orthogeomys heterodus cartagoensis_ (Goodwin, 1943). Amer. Mus.
Novit., 1227:2, April 22. Type from Paso Ancho, Province
Cartago, Costa Rica.
_Orthogeomys heterodus dolichocephalus_ (Merriam, 1895). N. Amer.
Fauna, 8:189, January 31. Type from San José, Costa Rica.
_Orthogeomys heterodus heterodus_ (Peters, 1865). Monatsb. preuss.
Acad. Wiss., Berlin, 1865:177. Type from Costa Rica, exact
locality unknown.
_Orthogeomys cavator nigrescens_ (Goodwin, 1943). Amer. Mus. Novit.,
1227:3, April 22. Type from El Muneco (Río Navarro), 10 mi. S
Cartago, 4000 ft., Province Cartago, Costa Rica.
_Orthogeomys cavator pansa_ (Bangs, 1902). Bull. Mus. Comp. Zool.,
39:44, April. Type from Bogava (= Bugaba), 600 ft., Chiriquí,
Panamá.
_Orthogeomys dariensis_ (Goldman, 1912). Smithsonian Misc. Coll.,
60(2):8, September 20. Type from Cana, 2000 ft., mountains of
eastern Panamá.
_Orthogeomys underwoodi_ (Osgood, 1931). Field Mus. Nat. Hist.,
Publ. 295, Zool. Ser., 185:143, Aug. 3. Type from Alto de
Jabillo Pirris, between San Geronimo and Pozo Azul, western
Costa Rica.
_Orthogeomys cherriei carlosensis_ (Goodwin, 1943). Amer. Mus.
Novit., 1227:3, April 22. Type from Cataratos, San Carlos,
Alajuela, Costa Rica.
_Orthogeomys cherriei cherriei_ (J. A. Allen, 1893). Bull. Amer.
Mus. Nat. Hist., 5:337, December 16. Type from Santa Clara,
Costa Rica.
_Orthogeomys cherriei costaricensis_ (Merriam, 1895). N. Amer.
Fauna, 8:192, January 31. Type from Pacuare, Costa Rica.
_Orthogeomys matagalpae_ (J. A. Allen, 1910). Bull. Amer. Mus. Nat.
Hist., 28:97, April 30. Type from Peña Blanca, Matagalpa,
Nicaragua.
Genus =Pappogeomys= Merriam
1895. _Pappogeomys_ Merriam, N. Amer. Fauna, 8:145, January 31.
1895. _Cratogeomys_ Merriam, N. Amer. Fauna, 8:150, January 31.
Type: _Geomys merriami_ Thomas.
1895. _Platygeomys_ Merriam, N. Amer. Fauna, 8:162, January 31.
Type: _Geomys gymnurus_ Merriam; Hooper, Jour. Mamm.,
27:397, November 25, 1946.
_Type._--_Geomys bulleri_ Thomas, 1892, from near Talpa, west slope
Sierra de Mascota, 8500 ft. (actually about 5000 ft.), Jalisco.
_Chronologic range._--Late Pliocene, from deposits of early Blancan
age (Benson local fauna, Arizona) to the Recent. However in the
Pleistocene, only late Pleistocene records are known, and
_Pappogeomys_ has not been found in early (late Blancan) or middle
(Irvingtonian) Pleistocene local faunas. Presumably the genus was
restricted to México during the Pleistocene until post-Wisconsin time.
_Description and discussion._--The size ranges from as little as in
the smaller kinds of _Thomomys_ to the maximum attained in the
subfamily and matched elsewhere perhaps in only a few of the larger
subspecies of _Orthogeomys grandis_. Depending on the species and
subgenus, the form of the skull varies from generalized to
specialized. The generalized skulls are short and not especially
narrow; the zygomatic arches are spread laterally so far that the
breadth across them exceeds the breadth across the mastoid processes.
The most specialized skulls are platycephalic and the breadth across
the mastoid processes equals or exceeds the breadth across the
zygomatic arches (even so, the zygomatic arches are still relatively
widespread). In correlation with the great breadth of the posterior
part of the cranium, the rami of the mandibles diverge widely
posteriolaterally and the angular processes are remarkably elongated.
The rostrum is moderately broad in most species, but not nearly so
broad and heavy as in _Orthogeomys_.
The single deep, median sulcus on the outer surface of the upper
incisor is slightly displaced to the inner side of the tooth. The
posterior surface of P4 lacks enamel (small vestige found on lingual
end of posterior wall in only two adult individuals--UA 3260 and KU
100442, of the subgenus _Pappogeomys_); the other three plates are
fully developed as usual. The p4 is provided with four fully developed
enamel plates, in the pattern characteristic of the tribe Geomyini. In
the p4 of the late Pliocene species (_P. bensoni_) the re-entrant
angles are open (obtuse), a trait that is evidently primitive in the
Geomyini.
All three lower molars are single, compressed, elliptical columns with
enamel on only the posterior surfaces. M1 and M2 are also elliptical
in cross-section and decidedly anteroposteriorly compressed, like the
lower molars. Nevertheless, the enamel pattern is variable; enamel
plates may be retained completely across both the anterior and
posterior walls of M1 and M2 or only the anterior plate may be
retained without reduction and the posterior plate may be reduced so
that only a vestige is retained on the lingual fourth of the tooth or
the posterior plate may be completely lost.