Evolution and Classification of the Pocket Gophers of the Subfamily Geomyinae Part 2

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 a.s.sumption 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).

_Th.o.m.omys umbrinus_ has been reported from San Josecito Cave, Nuevo Leon, Mexico (Russell, 1960:542); Upper Bercerra, Mexico (Hibbard, 1955a:51--identified only as _Th.o.m.omys_ sp., but undoubtedly referable to _T. umbrinus_). Post-Wisconsin remains of _Th.o.m.omys 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 _Th.o.m.omys_ from Wisconsin deposits in Hawver Cave, Eldorado County, California, but did not a.s.sign them to species.

Gilmore (1947:158) found the remains of _Th.o.m.omys umbrinus_ in cave deposits near Quatro Cienegas in central Coahuila. These cave deposits may have been laid down during the Wisconsin, but more likely acc.u.mulated 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, Mexico, 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 _Th.o.m.omys_ to the genus _Geomys_ in his revised list of Cope's earlier report on the Fossil Lake (or Silver Lake) fauna (see discussion of _Th.o.m.omys_ 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 s.e.x, 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 a.s.semblage, 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, Mexico. 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 Mexico. Two of these from San Josecito Cave in Nuevo Leon 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 p.r.o.ng 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 p.r.o.ng 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 princ.i.p.al 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) a.s.signed 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 a.s.semblage, 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 Redd.i.c.k 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 Redd.i.c.k I fauna as early Sangamon. Simpson (1928:2) reported _Geomys florida.n.u.s_ [= _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 florida.n.u.s_ [= _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 a.s.sumed that disjunction occurred as a result of Wisconsin glaciation. It is interesting to note that the genus _Th.o.m.omys_ 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 Mexico. 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 dent.i.tions. 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 Leon, Mexico, 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 relations.h.i.+ps.

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 Mexico. The Wisconsin age of these beds suggests an earlier Pleistocene derivation of the _gymnurus_-group of species.

Several specimens of the subgenus _Cratogeomys_ have been reported from beds of latest Wisconsin (certainly after the glacial maximum) or post-Wisconsin age. Gilmore (1947:158) found fossil remains of _Cratogeomys_ [= _Pappogeomys_] _castanops_ commonly in Quaternary cave deposits on the mountain slopes in the vicinity of Cuatro Cienegas, in central Coahuila. These deposits actually may be of post-Wisconsin origin (see discussion above). Alvarez (1964:8) obtained fragments of _Cratogeomys_ [= _Pappogeomys_] _tylorhinus_ from sub-Recent deposits of Capa III in the Cueva La Nopalera in southwestern Hidalgo, Mexico. _Pappogeomys merriami_ lives in the area today. Mayer-Oakes (1959:373) reported remains of _Cratogeomys_ [= _Pappogeomys_] _merriami_ from levels eight and eleven of the excavations at El Risco II, in the northern part of Mexico City. The ages of these deposits are unknown to me, but they probably are no older than late Wisconsin with most of the beds dating from the post-Wisconsin.

_Orthogeomys_

This genus is not known from the Pleistocene, except for its occurrence in the San Josecito cave deposits of southwestern Nuevo Leon, Mexico (Russell, 1960:544). Although _Orthogeomys_ does not occur in the immediate vicinity of the cave at the present time, the northern limits of its range is nearby in southern Tamaulipas. The _Orthogeomys_ from San Josecito Cave differs from living species, and has been named _Heterogeomys_ [= _Orthogeomys_] _onerosus_ Russell (_loc. cit._), and is evidently referable to the subgenus _Heterogeomys_. As mentioned before, the San Josecito Cave local fauna represents deposits of Wisconsin glaciation.

HISTORY OF CLa.s.sIFICATION

The account of the Tucan or Indian mole by Hernandez (sometimes listed as Fernandez) in 1651 probably is the earliest published one of a geomyid (see Merriam, 1895:201; Coues, 1877:607-608). Linnaeus in 1758 did not mention geomyids. In 1772, Kerr described Hernandez's Tucan under the name _Sorex mexicana_ on the basis of Hernandez's account without having seen any specimens. Lichtenstein in 1827 applied the technical name _Ascomys mexicana_ to three specimens collected by Deppe from unknown localities on the tableland of Mexico. Merriam (_loc. cit._) pointed out that the name _mexica.n.u.s_ of Lichtenstein in 1827 is a _nomen nudum_, and that it is preoccupied by _mexica.n.u.s_ used by Kerr in 1792. The latter can not be technically identified with any particular species of geomyid.

Bartram in 1791 wrote of the pocket gopher of Florida, without formally describing it. The first available technical name is _Mus bursarius_ of Shaw in 1800. Rafinesque in 1817 proposed the first generic names for the geomyids when he described _Geomys_ and _Diplostoma_. In 1839, Waterhouse referred the genus _Geomys_ to his family Arvicolidae, considered by him to be a subgroup of muroids. In 1841, he suggested that _Geomys_ was related to _Bathyergus_ and _Spalax_. Waterhouse in 1848 (p. 8) treated the pocket gophers as a subgroup of rodents under the group name Saccomyina, in which he included the genera _Heteromys_, _Saccomys_, _Perognathus_, and _Dipodomys_. Hence, Waterhouse was the first to recognize the relations.h.i.+p between the heteromyids and geomyids. In the next year Gervais erected the family Pseudostomidae for a group of specialized squirrels to include _Geomys_ and _Th.o.m.omys_ and the same genera (at least in part) of heteromyids that Waterhouse cla.s.sified in the "family" Saccomyina.

In 1839 the name _Th.o.m.omys_ was proposed by Maximilian (Wied-Neuwied).

All of the generic names previously proposed for pocket gophers were considered by subsequent authors to be synonyms of _Geomys_.

A third family name, Sciurospalacoides, was proposed by Brandt (1855:188) who referred _Geomys_ and _Th.o.m.omys_ to that family. He placed his new family phylogenetically between the family Sciuridae and the family Spalacoides (a group in which Brandt included the genera _Spalax_, _Sipheus_, and _Ellobius_). Brandt took exception to the cla.s.sification of Waterhouse (1848), who united the geomyids and heteromyids in one family. Brandt placed the heteromyid genera in other groups: _Perognathus_ in the Muridae, and _Macrocolus_ [= _Dipodomys_] in the Macrolini, a subfamily of the family Dipodoides.

Modern cla.s.sification of the pocket gophers begins with Baird in 1858.

The important cla.s.sifications are summarized in Table 1; a few that do not depart essentially from those listed have been omitted owing to limited s.p.a.ce for the tabular arrangement, but are discussed in the following account.

Baird probably was strongly influenced by the arrangement proposed by Waterhouse in 1848, but was opposed to separating geomyids from heteromyids as was done by Brandt. Baird was convinced of the close relations.h.i.+p of the geomyids and heteromyids, and referred both groups to one family, the Saccomyidae, as Waterhouse had done earlier. In order to recognize the morphological specializations he used two subfamilies, Geomyinae and the Saccomyinae. In the 20 years that followed, some authors followed Brandt and others followed Baird.

Gill, in 1872 (p. 71), proposed a cla.s.sification essentially like Baird's of 1858, but Gill raised Baird's subfamilies to the rank of family (see Table 1). In referring all pocket gophers to the Geomyidae, Gill used that name as a family term for the first time.

Also he established the superfamily Saccomyoidea to include his two families, Geomyidae and Saccomyidae; therefore, the Saccomyoidea was equivalent to the group Saccomyina of Waterhouse (1848) and the Saccomyidae of Baird (1858). Coues (1877), in his cla.s.sic monograph of the Geomyidae followed the arrangement proposed by Gill in treating the pocket gophers as a family. Alston in 1876 proposed another cla.s.sification based on Baird (1858), with two subfamilies, the Geomyinae and the Heteromyinae, united together in the family Geomyidae; thus, he recognized that the genus _Saccomys_ Frederic Cuvier, 1823, was a synonym of _Heteromys_ Desmarest, 1817, as had been pointed out by Gray (1868:201) and Peters (1874:356). Coues (1877:487-490) acknowledged the invalidity of the genus _Saccomys_, but refused to give up the name in supergeneric cla.s.sification. Winge, first in 1887 and subsequently in 1924, cla.s.sified the geomyids and heteromyids together in the family Saccomyidae as did Baird in 1858, and like Coues, Winge too ignored the synonymy of _Saccomys_ with _Heteromys_ and insisted on retaining the technical terms Saccomyidae and Saccomyini.

Up to the time of Merriam's cla.s.sic revision of the Recent Geomyidae in 1895 all the known species of living pocket gophers were referred to two genera, _Geomys_ and _Th.o.m.omys_. Merriam described much new material, especially from Mexico and Central America, and proposed seven new genera (see Table 1). His complete and detailed study of the dent.i.tions and osteology of the skull remains today as the definitive work on this subject, and is the point where most studies of the Geomyidae must begin. His treatment of the Recent genera survived for 52 years without change until Hooper (1946:397) arranged _Platygeomys_ as a synonym of _Cratogeomys_. However, Merriam's genera have been recognized in all subsequent cla.s.sifications except for the current review (see Table 1).

Cope described the first known fossil geomyids in 1878, and published an excellent review of the two genera, _Pleurolicus_ and _Entoptycus_, in 1884 (pp. 855-870, pl. 64, figs. 1-9). Both genera were recovered from the John Day Miocene deposits of Oregon. Cope did not propose a new systematic arrangement of these geomyids, but referred them to the family Saccomyidae and mentioned that the Saccomyidae was equivalent to the family Geomyidae of Alston. Winge, in 1887, followed Cope in referring _Pleurolicus_ and _Entoptycus_ to the Saccomyidae along with the living genera _Th.o.m.omys_ and _Geomys_. Miller and Gidley (1918), in their synopsis of the supergeneric groups of rodents, proposed a new subfamily, Entoptychinae, to include the divergent Miocene pocket gophers. Miller and Gidley also revived the old subfamily Geomyinae of Baird (1858), but restricted its application to the modern pocket gophers and their immediate ancestors. In 1936, A. E. Wood revised the taxa of the subfamily Entoptychinae, and described the first Miocene genus, _Dikkomys_, of the Geomyinae. He followed the supergeneric cla.s.sification of Miller and Gidley (1918).

The recent cla.s.sifications of Simpson (1945) and Wood (1955) have combined the cla.s.sifications of Merriam (1895) and Wood (1936). Wood (1955) brought up to date the list of genera, including those that were described after the publication of Simpson's cla.s.sification (1945). In Table 1, the list of genera is princ.i.p.ally from Simpson (1945) but generic names used by Wood (1955) are included. This is the currently accepted cla.s.sification.

The new cla.s.sification proposed in this paper (see Table 1) includes three tribes proposed as vertical units; they are intended to stress the phyletic trends in the known evolutionary sequences by placing immediate ancestors together with their descendants.