western North America, as follows: Burnet Cave, Gaudalupe Mt., New
Mexico (Schultz and Howard, 1935:280); Carpinteria Asphalt, California
(Wilson, 1933a:70); McKittrick Asphalt, Kern County, California (J. R.
Schultz, 1938:206); Rancho La Brea, Los Angeles County, California
(Dice, 1925:125--specimens described as a new subspecies, _T. b.
occipitalis_); Papago Springs Cave, Santa Cruz County, Arizona
(Skinner, 1942:150 and 158--probably _bottae_, but possibly _umbrinus_
on the assumption that the two are specifically instead of
subspecifically distinct); Isleta Cave, Bernalillo County, New Mexico
(Harris and Findley, 1964:115--some of these fossils may be
post-Wisconsin in age); Potter Creek Cave and Samwel Cave, Shasta
County, California (Sinclair, 1905:146--identified as _T. leucodon_,
now a subspecies of _T. bottae_; also see Hay, 1927:214-215).
_Thomomys umbrinus_ has been reported from San Josecito Cave, Nuevo
León, México (Russell, 1960:542); Upper Bercerra, México (Hibbard,
1955a:51--identified only as _Thomomys_ sp., but undoubtedly referable
to _T. umbrinus_). Post-Wisconsin remains of _Thomomys umbrinus_ are
reported by Alvarez (1964:6) from capa II and capa III of the Cueva La
Nopalera, southwestern Hidalgo. Hay (1927:222-223) reported specimens
of the genus _Thomomys_ from Wisconsin deposits in Hawver Cave,
Eldorado County, California, but did not assign them to species.
Gilmore (1947:158) found the remains of _Thomomys umbrinus_ in cave
deposits near Quatro Ciénegas in central Coahuila. These cave deposits
may have been laid down during the Wisconsin, but more likely
accumulated in the post-Wisconsin.
_Zygogeomys_
Remains found in the Curtis Ranch local fauna, Cochise County, in
southeastern Arizona are regarded as of middle Pleistocene age. See
Gazin (1942:481-484), Wilson (1937:39-40), Hibbard (1958:25), and
Hibbard _et al._ (1965:510-511). Although some question as to the
exact age of the Curtis Ranch local fauna still seems to exist, most
authorities on the Pleistocene agree that the age is not Pliocene and
that it is older than Rancholabrean. Gidley (1922:122) described the
pocket gopher found in the Curtis Ranch beds as _Geomys parvidens_,
which is preoccupied by _Geomys parvidens_ Brown (1908:194), a name
proposed for the pocket gopher from the Conard Fissure of Arkansas;
therefore, Hay (1927:136) proposed the name _Geomys persimilis_ for
the Curtis Ranch species to replace _Geomys parvidens_ Gidley.
_Geomys persimilis_ Hay became the type species of Gazin's genus
_Nerterogeomys_ (1942:507). In this paper, _Nerterogeomys_ is
considered to be a junior synonym of _Zygogeomys_.
_Zygogeomys persimilis_ is represented by a rostral fragment bearing
all the cheek teeth on the left side and the upper incisors. In
addition, two lower jaws, one with the first three cheek teeth,
are referred to the species (see Gazin, 1942:507). The fossils
identified as _Geomys_ from the Arroyo San Francisco, Cedazo fauna,
in Aguascalientes, México, by Mooser (1959:413) may be referable
instead to _Zygogeomys_. I have not seen the specimens and no figures
are available; Mooser states that a cranium was recovered. If either
the upper premolar or third molar is in place, generic identification
could be made with reasonable certainty. No other fossils of
_Zygogeomys_ have been uncovered in late Pleistocene deposits and the
significance of the absence of _Zygogeomys_ has been discussed in an
earlier paragraph of this section. _Geomys_ has not been found so far
south as Aguascalientes, but _Zygogeomys_ occurs farther south now and
presumably had a more extensive range on the plateau to the north in
the Pleistocene.
_Geomys_
_Geomys_ is common in Pleistocene deposits, especially on the Great
Plains. Certainly the center of differentiation for _Geomys_ was
in this region, although at times, probably when conditions were
favorable, _Geomys_ expanded its range into adjacent areas, reaching
the Pacific Coast in Irvingtonian times and the Atlantic Coast at the
time of the Illinoian glaciation. The earliest Pleistocene records
of the genus are from the Great Plains. McGrew (1944:49) described
_Geomys quinni_ from the Sand Draw local fauna, Brown County,
Nebraska, considered by Hibbard (1958:11) to be Nebraskan in age. As
mentioned in the account of Pliocene geomyids, _Geomys quinni_ occurs
also in the late Pliocene deposits of southwestern Kansas. Also,
_Geomys quinni_ occurs in the Broadwater-Lisco local fauna of Morrill
and Garden counties, western Nebraska (Barbour and Schultz, 1937:3;
Schultz and Stout, 1948:560-563; Schultz _et al._, 1951: table 1). The
Broadwater-Lisco is currently regarded as Aftonian deposits (Schultz
and Stout, _loc. cit._; Hibbard, 1958:11). Hibbard (1956:174)
identified _Geomys quinni_ from the Deer Park local fauna, probably
deposited during the early Aftonian interglacial, of Meade County,
Kansas. Strain (1966:36) described _Geomys paenebursarius_ on the
basis of fossils obtained from early Pleistocene deposits of the
Hudspeth local fauna from western Hudspeth County in the Trans-Pecos
of Texas. The Hudspeth fossils were probably deposited during the
Aftonian interglacial. From Kingman County, Kansas, Hibbard (_op.
cit._: 164) recovered isolated teeth of _Geomys_ from the Dixon local
fauna, regarded by him (_op. cit._:153-154) as deposited during the
latest Nebraskan glaciation, and correlated by him with the Sand Draw
local fauna of Nebraska. Hibbard (1958:11) later regarded the Dixon as
a transitional fauna between Nebraskan and Aftonian. The remains of
_Geomys_ from the Dixon are known only from isolated teeth. The teeth
are small, and suggest that a smaller species of _Geomys_ may have
occurred along with the more common and larger _G. quinni_ during the
early Pleistocene (see discussion beyond of the Saunders _Geomys_).
_Geomys quinni_ was widespread and common throughout the central Great
Plains from the late Pliocene (Rexroad fauna) through the early
Pleistocene (Nebraskan and Aftonian deposits).
Hibbard (1956:179) referred the pocket gopher remains taken from the
Saunders local fauna in Meade County, Kansas, to _Geomys tobinensis_,
a small species having continuous enamel bands around the lower
premolar in younger specimens. The Saunders local fauna was deposited
in the late Aftonian and is younger than the Deer Park local fauna
discussed above. Paulson (1961:138) later pointed out that the
Saunders _Geomys_ is distinct from _Geomys tobinensis_; hence, the
small pocket gopher from the Saunders local fauna is probably an
unnamed species, perhaps more closely allied to _paenebursarius_
than to _quinni_. The small _Geomys_ reported from the Aftonian
Broadwater-Lisco local fauna of Nebraska (Schultz and Stout, 1948:563)
may also be the same as the Saunders pocket gopher, but the smaller
adult specimens occurring in the same bed with larger specimens
probably are females and the larger specimens males. In all living
Geomyini females have smaller skulls than males.
The Irvingtonian provincial age is currently regarded as Middle
Pleistocene and includes the late Kansan glaciation (that part
occurring after the glacial maximum) and the Yarmouthian interglacial
(see Hibbard _et al._, 1965:512-514). The Irvingtonian provincial
age, therefore, follows the late Blancan provincial age of the early
Pleistocene and is succeeded by the Rancholabrean provincial age of
the late Pleistocene. No specimen of an Irvingtonian _Geomys_ is
referable to any living species. Two Irvingtonian species have been
described. Hibbard (1944:735) named _Parageomys tobinensis_ [= _Geomys
tobinensis_] from the Tobin local fauna of Russell County, Kansas.
This species since has been reported from the Cudahy local fauna of
Meade County, Kansas (Paulson, 1961:137). Hibbard (1956:183) also
identified as _Geomys tobinensis_ the pocket gopher recovered from the
Saunders local fauna, a late Aftonian deposit of Meade County, Kansas,
and reduced the technical name _Parageomys_ from generic to subgeneric
rank. Paulson (_op. cit._:138) pointed out that the Saunders specimens
differ from _G. tobinensis_, and he, therefore, restricted the name
to the small _Geomys_ of the Cudahy and Tobin local faunas of
Irvingtonian provincial age. _G. tobinensis_ is markedly smaller than
the Blancan _G. quinni_. The Cudahy and Tobin local faunas are of
approximately the same age, and presently both are included in one
unit, the Cudahy fauna. The Cudahy fauna is considered to have been
deposited in late Kansan as it occurs in strata immediately below the
Pearlette ash.
Recently, White and Downs (1961:8) described a new Irvingtonian
species, _Geomys garbanii_, from the middle Pleistocene Vallecito
Creek local fauna of San Diego County, California. Many well preserved
fossils of the new species were recovered. _Geomys garbanii_ is of
medium size (approximately the size of one of the larger subspecies of
_G. bursarius_), and significantly larger than the Irvingtonian
_Geomys tobinensis_ of the Great Plains. The Vallecito Creek
occurrence of _Geomys_ is the first authenticated record from the
Pacific Coast region. Matthew (1902:320) erroneously referred remains
of _Thomomys_ to the genus _Geomys_ in his revised list of Cope's
earlier report on the Fossil Lake (or Silver Lake) fauna (see
discussion of _Thomomys_ above).
A number of Irvingtonian fossil remains of _Geomys_ have not been
identified with particular species. Hibbard (1941a:206) found _Geomys_
in the Borchers local fauna (deposited in the time of the Yarmouthian
interglacial) of Meade County, Kansas. Also, _Geomys_ has been
reported from several sites in Nebraska. Schultz and Tanner (1957:67)
reported _Geomys_ from the Angus fossil quarry in Nuckolls County,
south-central Nebraska. The Angus fossils were found in sediments
of the Sappa Formation considered by Schultz and Tanner to be a
Yarmouthian deposit. Fossil quarries (Hay Springs, Rushville, and
Gordon) along the south side of the Niobrara River Valley in Sheridan
County, Nebraska, have also provided records of geomyids. Both a large
and small species of _Geomys_ have been reported from the more
recently excavated Rushville and Gordon sites (Schultz and Stout,
1948:562-567, and table 3). In view of the great disparity in size
owing to sex, these may actually be males and females of the same
species, as mentioned above. The name Hay Springs has been used in
reference to all three sites. The ages of the Hay Springs sites are
approximately the same, but their correlation is presently under
debate. Schultz and Tanner (1957:68-71) maintain that the fossils are
distinctly middle Pleistocene, and that they were deposited during
late Kansan glaciation, or perhaps from early Yarmouthian into early
Illinoian, with the largest concentration coming from the Sappa sands
of pre-Illinoian (Yarmouth) age. Hibbard (1958:25), basing his opinion
on the presence of _Microtus pennsylvanicus_, and the stage of
evolution of other species in the assemblage, regards the Hay Springs
sites as probably Illinoian deposits, but certainly no older than
that.
Mooser (1959:413) identified as _Geomys_ the pocket gopher from
Irvingtonian deposits in Arroyo San Francisco (loc. no. 5) near the
city of Aguascalientes, México. As suggested elsewhere in this
account, these fossils may be referable to _Zygogeomys_ rather
than _Geomys_. The Irvingtonian provincial age of this fauna was
established by Hibbard and Mooser (1963:245-250). Other alleged
occurrences have recently been compiled by Alvarez (1965:19-20).
Maldonado-Koerdell (1948:20) noted four fossil occurrences of the
genus _Geomys_ in México. Two of these from San Josecito Cave in
Nuevo León have since been identified with the genera _Orthogeomys_
and _Pappogeomys_ (Russell, 1960:543-548); the third listed by
Maldonado-Koerdell from "near Ameca, Jalisco," was based on Brown's
(1912:167) mention of some bones supposedly of the family "Geomyidae,"
and the fourth refers to pocket gopher remains from the "Hochtals von
Mexiko" listed as _Geomys_ by Freudenberg (1921:139). His generic
identification is doubtful and the specimens should be compared with
Mexican genera of the Geomyinae.
Upper Pleistocene records of _Geomys_ also are common. Upper
Pleistocene is here understood to include late Illinoian,
Sangamon and Wisconsin deposits; all are considered to be of
Rancholabrean provincial age (see Hibbard _et al._, 1965:512-515) and
post-Irvingtonian. The presence of remains of _Bison_ and/or _Microtus
pennsylvanicus_ are currently considered mammalian index fossils of
Rancholabrean faunas. In the Illinoian, _Geomys_ extended its range to
the Atlantic Coast in the southeastern United States. The eastern and
western species-groups evidently were isolated throughout much of the
late Pleistocene, and, therefore, evolved separately. Of the two, the
eastern, or _pinetis_, species-group seems to have remained somewhat
more generalized, and the western, or _bursarius_, species-group has
become more specialized. The Rancholabrean _Geomys_ from deposits in
the southeastern United States are referable (see Ray, 1963:325) to
_Geomys pinetis_.
Marsh (1871:121) described _Geomys bisulcatus_ from the North Prong of
the Loup River (near Camp Thomas), Nebraska. These beds are also
termed the Loup Fork or Loup River fossil beds (see discussion on p.
485), and they lie along the upper reaches of the Middle Loup River
in Thomas County (near Senea), Hooker County (near Mullen), and
southeastern Cherry County (probably the North Prong beds northwest
of Mullen). These beds were at first thought to be of Miocene age,
but later were regarded as early Pliocene (see Schultz and Stout,
1948:562-566 for a historical account of expeditions to these fossil
sites). Schultz and Tanner (1957:71-72) pointed out that the principal
fossiliferous beds in the Middle Loup region are of middle to late
Pleistocene age, with most of the fossils coming from the Crete sand
and silt beds which are probably early Illinoian deposits, and,
therefore, younger than the Hay Springs faunas. Some fossils may have
come from the Sappa deposits dated by Schultz and Tanner (_loc. cit._)
as mostly Yarmouthian deposits. _Geomys bisulcatus_, judging from
the original description and Hibbard's discussion of the cotypes
(1954:357), does not differ significantly from _Geomys bursarius_.
However, _Geomys bisulcatus_ is tentatively retained as a valid
species. Based on the evidence cited above it seems unlikely that
_Geomys bisulcatus_ occurred in pre-Irvingtonian times as often
suggested in the literature.
The genus _Geomys_ has been identified in several faunas of Illinoian
age, all from the Great Plains. Stephens (1960:1961) reported the
genus from the Doby Springs local fauna in Harper County, Oklahoma,
and Starrett (1956:1188) reported it from the Berends local fauna in
Beaver County, Oklahoma. Schultz (1965:249) assigned 21 isolated
teeth, including six incisors, from Butler Springs local fauna
(considered by him to be late Illinoian, following the glacial
maximum) to _Geomys_ cf. _bursarius_. Hibbard and Taylor (1960:167)
reported a baculum tentatively identified as that of _Geomys_ from the
early Illinoian Butler Springs local fauna (including the Adams fauna)
of Meade County, Kansas. Hibbard (1963:206) recorded the genus
_Geomys_ from the Mt. Scott local fauna (late Illinoian deposits) of
Meade County, Kansas; the specimens probably are referable to the
living species _bursarius_. From McPherson County, Kansas, Hibbard
(1952:7) reported the genus _Geomys_ from the Kentuck Assemblage,
which he (1958:25) regarded as a composite of Illinoian and Sangamon
species. Specific identification of the Illinoian pocket gophers is
uncertain, primarily due to the fragmentary nature of the material. On
the basis of dental characters alone most specimens could be referred
to _G. bursarius_; however the taxonomic status of _G. bisulcatus_
is in doubt, and more complete material may indicate that the
Illinoian gophers are specifically distinct from the living species.
Consequently, most authors, including myself, have made no attempt to
refer these specimens to species. Nevertheless, the Illinoian _Geomys_
from the Great Plains is more closely allied to the living species of
_Geomys_ than it is to the earlier Irvingtonian species.
_Geomys bursarius_ has been collected from a number of Sangamon fossil
sites on the Great Plains. Although specific identification of
specimens of _Geomys_ from Illinoian faunas is uncertain, the Great
Plains _Geomys_ from Sangamon and later deposits probably is referable
to the living species as Hibbard and Taylor (1960:165) pointed out.
They found no difference between _Geomys_ recovered from the Cragin
Quarry local fauna (early Sangamon) of Meade County, Kansas, and the
living species _Geomys bursarius_. Isolated teeth of the same species
were collected from the Jinglebob local fauna of Meade County, Kansas
(Hibbard, 1955b:206), a fauna of the late Sangamon. Hibbard (1943:240)
also recorded the genus _Geomys_ (referable to _G. bursarius_) from
the Rezabek local fauna of Lincoln County, Kansas. According to
Schultz _et al._ (1951:6 and table 1) the genus _Geomys_ occurs
in buried or "fossil" soils of Sangamon age, lying just above the
Loveland Loess, in Nebraska. No specific localities were given by
them, nor were any particular specimens mentioned. Dalquest reported
_Geomys bursarius_ from two Sangamon faunas in northern Texas. The
species is represented in the Ward Quarry local fauna of Cooke County,
Texas (1962a:42), and the Good Creek local fauna of Foard County,
Texas (1962b:575).
_Geomys bursarius_ has been reported from Wisconsin fossil deposits
of the Great Plains and adjacent areas as follows: Jones local fauna,
Meade County, Kansas (Hibbard and Taylor, 1960:64-66); Two Creeks
Forest beds of the third interstadial soils formed between Cary and
Mankato glaciations, late Wisconsin (Schultz _et al._, 1951:8 and
table 1); Cita Canyon local fauna in the northern part of the
Panhandle of Texas (Johnson and Savage, 1955:39); Howard Ranch local
fauna of Hardeman County in northwestern Texas (Dalquest, 1965:70);
Quitaque local fauna of Motley County, Texas (Dalquest, 1964:501);
Clear Creek local fauna of Denton County in north-central Texas
(Slaughter and Ritchie, 1963:120); Ben Franklin local fauna, of late
Wisconsin beds along the North Sulphur River in Delta County, NE Texas
(Slaughter and Hoover, 1963:137); Bulverde Cave (Hay, 1920:140;
1924:247) and Friesenhahn Cave (Tamsitt, 1957:321), both in Bexar
County, south-central Texas; Alton, Illinois (Hay, 1923:338-339);
Wisconsin drift of Illinois, without mention of specific locality
(Bader and Techter, 1959:172); Wisconsin drift of southwestern
Wisconsin and northeastern Iowa (Hay, _op. cit._:343); Wisconsin drift
near Galena, Illinois, and mouth of Platte River in eastern Nebraska
(Leidy, 1869:406).
Brown (1908:194) described _Geomys parvidens_ from the Conard Fissure,
in northern Arkansas. Hibbard (1958:25) concluded that the Conard
Fissure fauna represents a glacial stage, probably the Illinoian, and
Hibbard _et al._ (1965:510-511) regarded the fauna as a composite
including both Irvingtonian and Rancholabrean elements. White and
Downs (1961:21) considered _G. parvidens_ to be a subspecies of
_Geomys bursarius_.
The first Pleistocene occurrence of _Geomys_ in the southeastern
United States is from the Reddick I deposits reported by Gut and Ray
(1963:325), who found the remains of _Geomys pinetis_ among the
fossils comprising the "rodent beds" of Marion County, Florida. Gut
and Ray tentatively identified the beds as Illinoian, but Kurten
(1965:219) regarded the Reddick I fauna as early Sangamon. Simpson
(1928:2) reported _Geomys floridanus_ [= _pinetis_] from Saber-tooth
Cave deposits of Citrus County, Florida. The Saber-tooth Cave (or
Lecanto Cave) local fauna is considered by Kurten (_op. cit._:219)
also to be a Sangamon deposit. _Geomys floridanus_ [= _pinetis_] was
reported from the Seminole Field deposits by Simpson (1929:563); both
Simpson and Kurten (_op. cit._:221) agreed that the Seminole Field
fauna is mainly late Wisconsin, although sub-Recent fossils occur at
the tops of the beds. Ray (1958:430) collected remains of _Geomys
pinetis_ from the Melbourne Bone Bed of Brevard County, Florida. The
Melbourne local fauna is considered to be from Wisconsin deposits by
Kurten (_op. cit._:220). The eastern species of _Geomys_ were probably
derived from Great Plains stock that reached the southeastern Coastal
Plains in early Rancholabrean (Illinoian) time. Presently there is no
contact between the eastern and western populations of the genus, and
it is assumed that disjunction occurred as a result of Wisconsin
glaciation. It is interesting to note that the genus _Thomomys_
occurred in this region at approximately the same time; both genera
occur in Saber-tooth Cave deposits.
_Pappogeomys_
The genus _Pappogeomys_ is not known from Pleistocene deposits older
than the Wisconsin glaciation, but a pre-Pleistocene occurrence in the
Benson beds of Arizona (see discussion of the Pliocene above) shows
that _Pappogeomys_ had been differentiated by late Pliocene time.
The absence of _Pappogeomys_, beginning in the early Pleistocene and
continuing well into the late Pleistocene, is attributed to the
southern distribution of the genus, where its range probably was
centered on the Central Plateau of México. The paucity of early and
middle Pleistocene deposits from this critical region prevents any
definite statements about phyletic development within the genus. All
of the late Pleistocene records pertain to the subgenus _Cratogeomys_
(long in use as a generic name but in the present paper reduced to
subgeneric rank in the genus _Pappogeomys_). Schultz and Howard
(1935:280) found _Cratogeomys_ [= _Pappogeomys_] _castanops_ in
Burnett Cave in the Guadalupe Mountains of south-central New Mexico.
The Burnett deposits are probably late Wisconsin (see Schultz and
Tanner, 1957:75, for discussion of the age of these deposits based
on carbon-14 tests). These writers (_loc. cit._) also referred
the mandible of a small pocket gopher to the genus _Pappogeomys_
[= subgenus _Pappogeomys_]. However, neither genera nor subgenera of
the tribe Geomyini can be distinguished on the basis of their inferior
dentitions. Judging from the distribution of the modern geomyines, it
seems unlikely that the subgenus _Pappogeomys_ has occurred beyond its
present range in the late Pleistocene; therefore the small mandible is
most likely that of a young individual of _Pappogeomys castanops_.
Russell (1960:543) referred specimens collected at San Josecito Cave
in Nuevo León, México, to the group of small subspecies _Cratogeomys_
[= _Pappogeomys_] _castanops_. Also, Russell (_loc. cit._) identified
a rostral fragment as of the genus _Cratogeomys_ [= subgenus
_Cratogeomys_] although the fragment had a combination of features
different than in any named species of the genus; he did not name the
fragment as a new species, preferring to wait for additional material
that could clarify its taxonomic relationships.
Hibbard (1955a:52-53) identified _Cratogeomys_ [= _Pappogeomys_]
_tylorhinus_ from the Becerra Superior deposits in the valley of
Tequixquic in the northern part of the state of México. The Wisconsin
age of these beds suggests an earlier Pleistocene derivation of the
_gymnurus_-group of species.