Part 3

Three extinct species of _Thomomys_, all referable to the subgenus _Thomomys_, have been described. _Thomomys microdon_ Sinclair (1905:146), based on the rostral portion of a skull without a mandible, is from the Potter Creek Cave local fauna, Shasta County, California, and has been recovered also from Samwel Cave, Shasta County, California. _T. microdon_ closely resembles _Thomomys monticola_ that lives in the area today. _Thomomys scudderi_ Hay (1921:614) is from the Fossil Lake (or Christmas Lake) local fauna in central Oregon. Elftman (1931:10-11) referred these specimens to _Thomomys townsendii_, and he considered _T. scudderi_ to be a synonym of _T. townsendii_. Davis (1937:156-158) disagreed with Elftman concerning the taxonomic status of _T. scudderi_, which he regarded as a valid species. According to Davis, _T. scudderi_ is more closely allied to _Thomomys bottae_ than to _T. townsendii_. Cope (1878:389; 1889:160-165) had referred the same specimens to _Thomomys clusius_ (now _Thomomys talpoides clusius_). Cope considered the beds to be Pliocene in age. In all accounts of the Fossil Lake local fauna up to Hay (1921), the specimens of _Thomomys_ were referred to the species _clusius_, _talpoides_, or _bulbivorus_ (see Elftman, _loc. cit._). The Fossil Lake local fauna is currently considered as being of Rancholabrean provincial age, probably dating from the Wisconsin glacial maximum when the lake reached its greatest size. The third extinct species described from the Wisconsin is _Thomomys vetus_ Davis (1937:156), also from the Fossil Lake local fauna in Lake County, Oregon. Davis pointed out that _T. vetus_ differs from _T. scudderi_ Hay, of the same fauna, in larger size and other cranial details, and that it is closely allied to the living species _Thomomys townsendii_, and not to _Thomomys talpoides_, which is the only species of _Thomomys_ living in the area today.

_Thomomys townsendii_ was recovered by Gazin (1935:299) from the American Falls beds (probably Wisconsin deposits) in Idaho.

_Thomomys talpoides_ is reported from the Howard Ranch local fauna in Hardeman County, western Texas, by Dalquest (1965:69-70), who referred the isolated teeth to _T. talpoides_ on geographic grounds, apparently on the erroneous assumption that _T. talpoides_ was the species of _Thomomys_ nearest geographically to Hardeman County. Hay (1927:259) reported _Thomomys fuscus_ [= _Thomomys talpoides_] from late Pleistocene beds near Wenatchee, Chelan County, Washington. Hibbard (1951:229) recorded _Thomomys talpoides_ from late Pleistocene deposits in Greeley County, Kansas, and Walters (1957:540) reported the same species from late Pleistocene deposits in Clark County, Kansas. According to Hibbard (1958:14) other remains reported as _T. talpoides_ have been recovered from numerous areas of Wisconsin glacial drift in western North America.

_Thomomys bottae_ has been identified from Wisconsin age deposits in 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_