Thomomys perpallidus aureiventrisHall, Univ. California Publ. Zoöl., 32:444, July 8, 1930; Univ. California Publ. Zoöl., 37:3, April 10, 1931.Thomomys bottae aureiventrisGoldman, Proc. Biol. Soc. Washington, 48:156, October 31, 1935.
Thomomys perpallidus aureiventrisHall, Univ. California Publ. Zoöl., 32:444, July 8, 1930; Univ. California Publ. Zoöl., 37:3, April 10, 1931.
Thomomys bottae aureiventrisGoldman, Proc. Biol. Soc. Washington, 48:156, October 31, 1935.
Type.—Male, adult, skin and skull, No. 43980, Museum of Vertebrate Zoölogy, University of California; Fehlman Ranch, 3 mi. N Kelton, 4,225 ft., Box Elder County, Utah; September 27, 1929; collected by Louise Kellogg; original number 451.
Range.—Northwestern Utah, and extreme western Utah as far south as the southern end of the Deep Creek Mountains.
Diagnosis.—Size medium (see measurements); claws on front feet small. Color: Near Cinnamon on dorsal and ventral surfaces; inguinal region, front and hind feet and distal third to half of tail white; nose, cheeks and postauricular patches grayish black. Skull: Moderately angular and ridged; zygomatic arches nearly parallel with sides of skull; jugals vertical; marked thickening at union of jugal and zygomatic process of maxilla; greatest zygomatic breadth at anterior part of arches; interpterygoid space lyre-shaped; ventral margin of jugal concave dorsally; nasals long and denticulate distally; parietal ridges bowed in at two places, at coronal suture and at middle of interparietal; paroccipital processes extremely well developed; dorsal frontomaxillary suture usually straight.
Comparisons.—From near topotypes ofThomomys bottae centralis,aureiventrisdiffers as follows: Size larger; tail shorter; hind foot longer; claws on front feet shorter. Color: Slightly darker on upper parts, but with greater extension of white on ventral surface. Skull: Zygomatic breadth greater; greatest width across zygomatic arches at anterior rather than posterior region; zygomatic arches thicker at union of jugals and zygomatic processes of maxillae; dorsal frontomaxillary suture less convex medially; mastoid breadth greater; extension of premaxillae posterior to nasals less; interpterygoid space lyre-shaped rather than V-shaped.
From topotypes ofThomomys bottae albicaudatus,aureiventriscan be distinguished by: Size larger; hind foot longer. Color: Markedly lighter throughout, Cinnamon as opposed to near (13''''n) Black. Skull: Larger in all but three measurements taken; extension of premaxillae posterior to nasals less; alveolar length of upper molar series shorter; zygomatic arches widest anteriorly rather than posteriorly; thickening at union of jugal and zygomatic process of maxilla markedly greater; interpterygoid space lyre-shaped as opposed to V-shaped; lacrimal processes more globose at tips.
Thomomys bottae aureiventriscan be readily distinguished fromT. b. bonnevillei,sevieri,wahwahensis, andconvexusby larger size in all measurements taken and darker coloration. The same differences obtain in comparison withT. b. tiviusandstansburyiexcept thataureiventrisis much lighter colored. See comparisons under those forms.
Remarks.—T. b. aureiventrishas one of the most extensive ranges of any race ofT. bottaeoccurring in Utah. The range extends from the valleys of the northwest corner of the state south along the extreme western margin of the state approximately to the southern end of the Deep Creek Mountains. This ascribed range practically bounds the northwest and western margins of the great salt desert in Box Elder and Tooele counties. As far as known, this great waste area harbors no members of the Geomyidae. Pocket gophers were available from four localities in addition to the type locality. In these four localities all of the animals were intergrades. The three specimens from Queen of Sheba Canyon, Deep Creek Mountains, although smaller thanaureiventrisin every measurement taken, resemble it in color and general configuration of the skull. The animals from Trout Creek and Ibapah at the southern end of the range, although referred toaureiventris, are intermediate between it andcentralis. In color and measurements they more closely resemblecentralis, but the skulls closely resemble those ofaureiventris. The skulls show some slight characteristics ofbonnevillei, the form to the east, which indicate an early relationship between the two. Specimens from the east side of Tecoma Range, adjacent to Pilot Peak, although referred toaureiventrisare intergrades between it andcentralis. Although this locality is nearer the type locality ofaureiventristhan any of the other record stations, the animals show the maximum departure from topotypes in morphological features. In color they approachcentralis, and agree with it in one-half of the measured characters. The general configuration of the skull and a majority of the critical diagnostic characters, for example,jugal thickening, are more nearly as inaureiventris. From the above remarks it is readily understood that this subspecies is extremely variable.
Specimens examined.—Total, 55, distributed as follows:Box Elder County: Fehlman Ranch, 3 mi. N Kelton, 4,255 ft., 8 (7, M. V. Z.); Utah-Nevada Boundary, E Side Tecoma Range, 4,300 ft., 12.Tooele County: Ibapah, 5,000 ft., 21.Juab County: Queen of Sheba Canyon, W side Deep Creek Mountains, 5,600 ft., 11.
Specimens examined.—Total, 55, distributed as follows:Box Elder County: Fehlman Ranch, 3 mi. N Kelton, 4,255 ft., 8 (7, M. V. Z.); Utah-Nevada Boundary, E Side Tecoma Range, 4,300 ft., 12.Tooele County: Ibapah, 5,000 ft., 21.Juab County: Queen of Sheba Canyon, W side Deep Creek Mountains, 5,600 ft., 11.
Type.—Male, adult, skin and skull, No. 2726, Museum of Zoölogy, University of Utah; Orr's Ranch, Skull Valley, 4,300 ft., Tooele County, Utah; June 19, 1938; collected by S. D. Durrant; original number 1583.
Range.—Skull Valley, Tooele County, Utah.
Diagnosis.—Size medium (see measurements); tail short; hind foot short. Color: In a series of 24 animals, upper parts vary from Pale Smoke Gray (4 specimens) through Cinnamon Buff (19 specimens) to Dark Mouse Gray (1 specimen). The Cinnamon Buff color is considered to be typical. Color grading to lighter on underparts; postauricular patches small and grayish black; front and hind feet and distal part of tail white. Skull: Small, flat and heavily ridged; nasals short; zygomatic arches heavy and widely spreading, widest posteriorly at union of jugal and squamosal; union of jugal and zygomatic process of maxilla thickened, with a ventrally directed spinous process in sixty percent of the specimens; occasionally there is a second process, also directed ventrally at union of jugal and zygomatic process of squamosal; zygomatic arches convex dorsally; deep dorsal depression present in frontal bones in mature specimens; lacrimal processes prominent, projecting well above the arch at the anteromedial angle of the orbit; interpterygoid spaces V-shaped; tympanic bullae well inflated ventrally; upper incisors short, and pale; when placed on a flat plane the dorsal surface of the skull is nearly parallel to the substratum; space enclosed within the zygomatic arches nearly quadrangular.
Comparisons.—From topotypes ofThomomys bottae aureiventris,robustuscan be distinguished as follows: Size smaller; tail and hind foot shorter. Color: Lighter throughout. Skull: Smaller, more heavily ridged and more nearly flat; nasals shorter; rostrum relatively wider and shorter; zygomatic arches shorter and relatively more widely spreading with greatest width posteriorly as opposed to anteriorly; junction of jugal and zygomatic process of maxilla not as prominent;aureiventrisshows no spinous process at this junction; lacrimal processes larger and projecting farther dorsally; enclosed space within zygomatic arches roughly quadrangular as opposed to triangular; mastoidal part of tympanic bullae less exposed; sphenorbital fissure smaller; interpterygoid space V-shaped rather than lyre-shaped; palatal pits smaller and shallower; tympanic bullae smaller, but more inflated ventrally; basioccipitalaveraging relatively wider; molars smaller; upper incisors shorter, smaller and cadmium yellow as opposed to orange yellow.
Comparisons ofrobustuswith topotypes ofThomomys bottae albicaudatusshow the following: Size smaller. Color: Lighter throughout; postauricular patches smaller and lighter. Skull: Smaller, more compact and more nearly flat; rostrum shorter and more nearly straight; lacrimal processes larger, projecting higher above the anteromedial angle of the orbit; parietal ridges uniformly heavier; mastoid width actually as well as relatively wider; zygomatic arches heavier and relatively much wider (males 76.2 percent of basilar length, females 73.8 percent as opposed to males 73.8 percent and females 73.5 percent); union of jugal and zygomatic process of maxilla uniformly more thickened; spinous process at jugal-maxillary suture present; zygomatic arches much more concave on ventral surface; uniform deep depression present in mature adults, between frontal processes of premaxillae, and anterior interorbital region of frontals; extension of premaxillae posterior to nasals less; sphenorbital fissure more constricted; tympanic bullae more inflated ventrally, extending well ventrad of basioccipital; palatal pits shallower and smaller; molars smaller; upper incisors shorter, narrower and paler (see comparison ofaureiventris).
From near topotypes ofThomomys bottae centralisfrom 1 mile east of Garrison, Millard County, Utah,robustusdiffers in: Size smaller; tail and hind foot shorter. Color: Lighter, terminal bands of hair cinnamon, but because more black in underfur the animals appear darker; postauricular patches smaller and lighter. Skull: Shorter, more nearly flat and much more heavily ridged; nasals shorter; rostrum shorter and wider; lacrimal processes larger and projecting higher above anteromedial angle of orbit; zygomatic arches heavier, shorter, more angular and actually as well as relatively wider; jugals thicker; angle between maxillary plate and rostrum less obtuse; spinous process at jugal-maxillary suture present; extension of premaxillae posterior to nasals less; parietal ridges much more pronounced; looked at from above, space enclosed within zygomatic arches more quadrangular in shape as opposed to roughly triangular; tympanic bullae more inflated ventrally; molars smaller; upper incisors shorter, narrower and paler.
The characters that distinguishrobustusfrom topotypes ofThomomys bottae wahwahensisare: Size slightly smaller. Color: Darker throughout. Skull: Rostrum longer and narrower; nasalslonger; zygomatic arches wider and longer; lacrimal processes larger and projecting higher above anteromedial angle of the orbit; parietal ridges more roughened; tympanic bullae much larger and more inflated ventrally; supraoccipital higher; middorsal depression in frontals present. For comparisons withThomomys bottae bonnevilleisee account of that form.
The remaining forms from the Bonneville Basin, namely,Thomomys bottae sevieri,convexus,tiviusandstansburyiare all easily distinguished fromrobustus. Specimens ofsevieriare paler, smaller in every measurement taken, and the skulls are weaker and less angular. All specimens ofconvexusare paler, the skulls are more convex dorsally and narrower, with less ridging and angularity. Bothtiviusandstansburyiare small dark forms, with weak, smooth, small skulls as compared withrobustuswhich is light colored and has compact, ridged and angular skulls.
Remarks.—Twenty-three specimens were obtained at a small isolated spring. Critical study of animals taken only a few miles to the east prove them to be so different as to be referable to another subspecies,albicaudatus.T. b. robustusis an endemic form in this desert valley. The variable color is noteworthy but difficult to explain in an isolated population as small as this one. All five of the gray animals are females of which four are lactating adults. The affinities of this subspecies are withalbicaudatusto the east, but enough time has elapsed since isolation to enable them to differentiate.
Specimens examined.—Total, 23, from the type locality.
Specimens examined.—Total, 23, from the type locality.
Thomomys bottae minimusDurrant, Proc. Biol. Soc. Washington, 52:161, October 11, 1939; Marshall, Journ. Mamm., 21:154, May 14, 1940.
Thomomys bottae minimusDurrant, Proc. Biol. Soc. Washington, 52:161, October 11, 1939; Marshall, Journ. Mamm., 21:154, May 14, 1940.
Type.—Male, adult, skin and skull, No. 263942, U. S. National Museum (Biological Surveys Collection); Stansbury Island, Great Salt Lake, Tooele County, Utah; June 25, 1938; collected by William H. Marshall; original number 141.
Range.—Known only from the type locality.
Diagnosis.—Size small (see measurements); tail relatively long. Color: Upper parts Pinkish Buff, darker on head; underparts Pale Pinkish Buff; front and hind feet white; nose, chin and postauricular patches black. Skull: Long, slender and nearly devoid of ridges; braincase moderately inflated; interparietal quadrangular; zygomatic arches weak, widest in temporal region, but neither widely spreading nor angular; nasals straight and truncate posteriorly; extension of premaxillae posterior to nasals relatively great; tympanic bullae moderately inflated; palatal pits deep; rostrum short but narrow;interpterygoid space moderately lyre-shaped; upper incisors narrow; molars light.
Comparisons.—Compared with topotypes ofThomomys bottae albicaudatus,minimusdiffers as follows: Size markedly smaller; claws on front feet shorter and weaker. Color: Markedly lighter throughout, being Pinkish Buff as contrasted with near (13''''n) Black. Skull: Smaller in every measurement taken; slender, smooth, weak and nonangular as opposed to ridged, robust, wide and angular; zygomatic arches much weaker and not so widely spreading posteriorly; ascending processes of premaxillae much narrower; extension of premaxillae posterior to nasals less; interpterygoid space moderately lyre-shaped as opposed to V-shaped; dentition lighter.
Topotypes ofminimusdiffer from those ofThomomys bottae aureiventrisas follows: Size markedly smaller. Color: Lighter dorsally and no "gold color" on underparts. Skull: Markedly smaller in every measurement taken; weak, smooth and slender as opposed to ridged, angular and robust; zygomatic arches weak and widest posteriorly rather than heavy and widest anteriorly; no great thickening at region of union of jugal and zygomatic process of the maxilla; jugals more nearly straight rather than concave laterally; interpterygoid space not so markedly lyre-shaped; dentition lighter.
The races nearest geographically tominimusareThomomys bottae nesophilusandT. b. stansburyi. For comparisons see accounts of those forms.
Remarks.—This subspecies is the smallest of all the races ofThomomys bottaeoccurring in Utah. As far as known it is endemic to Stansbury Island, and since the Pleistocene Lake Bonneville attained its highest level has remained on that part of Stansbury Island that was above this high level. (See comments undernesophilus.) The sandy nature of the soil and the desert conditions of the area that has since been exposed at lower levels apparently do not constitute a favorable environment. Unlikenesophilusfrom Antelope Island, this form does not have its affinities withalbicaudatus, the valley form of the adjacent mainland, but does show affinities withstansburyi, the nearest mountain form on the mainland. This is easily understood when one realizes that Stansbury Island is only an isolated part of Stansbury Mountain that projects northward as a peninsula into Great Salt Lake. Thehistory of Stansbury Island with reference to isolation ofminimusparallels that ofnesophiluson Antelope Island. See discussion undernesophilus.
Specimens examined.—Total, 5, as follows:Tooele County: Stansbury Island, Great Salt Lake, 5 (U. S. N. M.).
Specimens examined.—Total, 5, as follows:Tooele County: Stansbury Island, Great Salt Lake, 5 (U. S. N. M.).
Thomomys bottae nesophilusDurrant, Bull. Univ. Utah, 27 (No. 2):2, October, 1936; Marshall, Journ. Mamm., 21:156, May 14, 1940.
Thomomys bottae nesophilusDurrant, Bull. Univ. Utah, 27 (No. 2):2, October, 1936; Marshall, Journ. Mamm., 21:156, May 14, 1940.
Type.—Male, adult, skin and skull, No. 1136, Museum of Zoölogy, University of Utah; Antelope Island, Great Salt Lake, Davis County, Utah; April 20, 1935; collected by S. D. Durrant; original number 761.
Range.—Known only from the type locality.
Diagnosis.—Size medium (see measurements); claws on front feet long. Color: Upper parts Cinnamon Buff; lighter below; sides Pinkish Buff interspersed with gray; pectoral and inguinal regions Cinnamon; nose grayish black; postauricular patches black. Skull: Interparietal wedge-shaped; tympanic bullae small; dorsal surface of lambdoidal prominence 3 mm. wide rather than developed as a crest; jugals nearly straight; zygomatic arches strongly rectangular.
Comparisons.—Compared with topotypes ofThomomys bottae albicaudatus,nesophilusis of approximately the same size, but differs as follows: Claws on front feet longer. Color: Lighter throughout; tail white terminally, but much darker at base; postauricular patches smaller. Skull: Interparietal wedge-shaped as opposed to roughly quadrangular; lambdoidal eminence more of a crest than a ridge; tympanic bullae smaller; jugals more nearly straight; zygomatic arches more nearly rectangular.
From topotypes ofThomomys bottae aureiventris,nesophilusdiffers in: Size smaller; claws on front feet longer. Color: Darker throughout; postauricular patches larger. Skull: Heavier, more massive; zygomatic arches more robust and convex laterally rather than concave; interparietal wedge-shaped rather than roughly quadrangular; braincase more nearly flat; tympanic bullae markedly smaller; upper molariform series longer; molariform teeth wider and heavier; interpterygoid space V-shaped rather than lyre-shaped.
The race nearest geographically tonesophilusisT. b. minimusfrom Stansbury Island, Great Salt Lake. It can easily be distinguished fromminimusby the following features: Size much larger; claws on front feet longer and thicker. Color: Darker throughout; postauricular patches larger and with more admixture of buff coloredhairs. Skull: Larger in every measurement taken; wide and robust as opposed to narrow and slender; zygomatic arches more widely spreading and angular; braincase more nearly flat; tympanic bullae actually larger, but relatively smaller; lambdoidal eminence flat-topped rather than a crest; interparietal wedge-shaped as opposed to quadrangular; teeth larger.
Remarks.—The affinities ofnesophilusof Antelope Island are unquestionably withalbicaudatusof the eastern and southern mainland. At the time of this writing (1945), Antelope Island is not truly an island, but only the tip of a broad peninsula projecting westward into Great Salt Lake. Nevertheless, the area of occurrence ofnesophilusis effectively isolated by the exposed, sandy lake bottom that is unsuited to occupancy by pocket gophers. Fluctuations in the level of the Great Salt Lake have broken and reëstablished this connection with the mainland many times. Each of the several other kinds of mammals which are known from both the island and the mainland show no differentiation on the island. These are kinds (see Marshall, 1940:156), which more freely cross the exposed, sandy lake bottom. I, myself, have noted tracks of coyotes going to and from the island. The pocket gopher,nesophilus, so far as known is the only mammal which has developed a subspecies endemic to the island. The beach levels of Pleistocene Lake Bonneville are well marked on both Antelope Island and Stansbury Island, which is fifteen miles west of Antelope Island. On the eastern side of Antelope Island the lower beach levels of this prehistoric lake are farmed. Although sought for elsewhere on this island, pocket gophers were found only in the farmed land. On Stansbury Island there has been no farming, and the endemic pocket gophers,minimus, although sought for elsewhere on that island were found only above the highest beach levels of the ancient lake. Evidently these pocket gophers still occupy only that part of Stansbury Island that projected above water during the greatest height of Lake Bonneville. Farming on Antelope Island may have developed a more favorable environment for pocket gophers, thus causing them to move down to the lower levels from that part of the island that was above water during Pleistocene times.
Specimens examined.—Total, 5, from the type locality.
Specimens examined.—Total, 5, from the type locality.
Type.—Female, adult, skin and skull, No. 2045, Museum of Zoölogy, University of Utah; South Willow Creek, Stansbury Mountains, 7,500 ft., Tooele County, Utah; July 2, 1937; collected by O. S. Walsh and S. D. Durrant; original number 1257 of Durrant.
Range.—Stansbury Mountains, Tooele County, Utah.
Diagnosis.—Size small (see measurements). Color: Upper parts Saccardo's Umber, darker on head; sides and underparts Pinkish Buff; nose, chin and postauricular patches black; front and hind feet and distal third to half of tail white. Skull: Small, slender, weak and smooth; zygomatic arches light and not widely spreading; zygomatic arches actually as well as relatively short; interparietal generally quadrangular; nasals relatively long and slender; interpterygoid space narrowly V-shaped; basioccipital fairly wide; tympanic bullae moderately inflated ventrally; dentition light.
Comparisons.—Topotypical specimens ofstansburyican be readily distinguished from those ofThomomys bottae centralis,aureiventrisandalbicaudatusby being smaller in every measurement taken, particularly those of the skull; the skull is weaker and smoother. In colorstansburyiis likealbicaudatusbut is much darker throughout thanaureiventrisandcentralis.
Comparisons of topotypes ofstansburyiwith those ofThomomys bottae sevierishow them to be of approximately the same size, but to differ as follows: Color: Darker throughout. Skull: Zygomatic arches shorter; tympanic bullae less inflated ventrally; zygomatic breadth less; mastoid breadth greater; width across alveolar processes of maxillae greater; alveolar length of upper molar series greater; molariform teeth larger.
Compared with topotypes ofThomomys bottae minimus,stansburyiis seen to be of larger size and darker color throughout, with a skull that is larger in most every measurement taken, although of the same slender, smooth, nonangular type.
Among named races ofThomomys bottae,stansburyimost closely resembles tivius, a small, dark, mountain form from central Utah. Size and color are almost the same butstansburyidiffers in: Tail shorter; hind foot averaging slightly longer. Skull: Generally larger in every measurement taken; zygomatic arches shorter; width across alveolar processes of maxillae greater; zygomatic arches more widely spreading, and widest in extreme posterior region rather than in region of jugal-squamosal suture.
Remarks.—The Stansbury Mountains are separated from the Oquirrh Mountains by the Stockton Bar, and from the Onaqui Mountains, which are in reality a continuation of the StansburyMountains, by only a low pass. Pocket gophers from Clover Creek, Onaqui Mountains and Little Valley, Sheeprock Mountains, although intergrades betweenrobustusandalbicaudatusare dark in color likestansburyi. These intergrades are large, dark colored, and have heavy, ridged, angular skulls. It appears thatstansburyiis a mountain subspecies derived fromalbicaudatusof the valley. It would be instructive to artificially transplant gophers from mountains to valleys, andvice versa, so as to reveal what effects if any on the animals' morphology the environment might have in one or a few generations. Gophers are well known to be very plastic, and such an experiment as suggested might call for modification of the view, held here, that the differential features of gophers from South Willow Creek and, say, Bauer, are hereditary.
Specimens examined.—Total, 11, from the type locality.
Specimens examined.—Total, 11, from the type locality.
Thomomys perpallidus albicaudatusHall, Univ. California Publ. Zoöl., 32:444, July 8, 1930; Univ. California Publ. Zoöl., 37:3, April 10, 1931.Thomomys bottae albicaudatusGoldman, Proc. Biol. Soc. Washington, 48:156, October 31, 1935; Durrant, Bull. Univ. Utah, 28 (No. 4):5, August 18, 1937.Thomomys perpallidus aureiventrisHall, Univ. California Publ. Zoöl., 37:3, April 10, 1931.
Thomomys perpallidus albicaudatusHall, Univ. California Publ. Zoöl., 32:444, July 8, 1930; Univ. California Publ. Zoöl., 37:3, April 10, 1931.
Thomomys bottae albicaudatusGoldman, Proc. Biol. Soc. Washington, 48:156, October 31, 1935; Durrant, Bull. Univ. Utah, 28 (No. 4):5, August 18, 1937.
Thomomys perpallidus aureiventrisHall, Univ. California Publ. Zoöl., 37:3, April 10, 1931.
Type.—Male, adult, skin and skull, No. 43971, Museum of Vertebrate Zoölogy, University of California; Provo, 4,510 ft., Utah County, Utah; October 17, 1929; collected by Annie M. Alexander; original number 506.
Range.—From the area between the Great Salt Lake and the Wasatch Mountains south along the western margin of the central mountains of the state to the Sevier River, in Juab County, west into Tooele County to the Onaqui and Sheeprock mountains.
Diagnosis.—Size medium (see measurements); claws on front feet medium. Color: Upper parts near (13''''n) Black, grading over sides and flanks to Pinkish Cinnamon on underparts; chin, nose, top of head and postauricular patches black; front feet, hind feet and distal third to half of tail white. Skull: Angular and ridged; zygomatic arches moderately wide spreading, widest posteriorly; paroccipital processes weak; zygomatic processes of maxillae convex anteriorly; lacrimal processes small and peglike; jugals convex dorsally on ventral surface; nasals short, rounded distally and truncate proximally; parietal crests bowed in, in two places; interpterygoid space broadly V-shaped.
Comparisons.-For comparisons ofalbicaudatuswithThomomys bottae aureiventrisandcentralissee accounts of those forms.
Topotypes ofalbicaudatusare dark colored and can be distinguished from those ofThomomys bottae birdseyei,tivius,stansburyiandcontractuswhich are also dark forms, by larger size and larger, more robust skulls (see accounts of those forms). It can bedistinguished from the remainder of the known subspecies ofThomomys bottaein Utah by darker color and by cranial details (see accounts of those forms).
Remarks.—The range ofalbicaudatusis larger than that of any other race ofThomomys bottaelimited to Utah. Specimens are available from thirty localities which represent widely varied habitats and environments. This subspecies consists of many highly variable local populations, and the marginal populations intergrade freely with adjacent races. In many populations, it is really difficult to recognize the relationships on account of the great variation, and one is frequently tempted to name some of them as distinct. Careful study of the large number of specimens has enabled me to recognize diagnostic characters common to all of these variable populations. The animals range from large and dark at the north to small and light at the south.
The Jordan River bisects Salt Lake County from north to south. Pocket gophers were taken at nine places east of the river, and at three places west of it.
Gophers from Salt Lake City and environs (east of the river) vary in color from almost black to dark cinnamon. Specimens from Draper, which locality is likewise east of the river, are uniformly lighter, but also vary in color. The skulls of animals from both localities are indistinguishable from each other and closely resemble those of topotypes. Specimens from the west side of the river, from Riverton, two miles west of Murray and Rose Canyon, Oquirrh Mountains, all are lighter in color than topotypes. The color varies from darkest at the north at Murray to lightest at the south at Riverton. This is exactly the reverse of what would be expected since Riverton is the locality geographically nearest to the type locality, Provo. The skulls are quite uniform and are all referable toalbicaudatus. The Jordan River may be one factor which causes this lack of uniformity between the animals from the two sides of the river. Davis (1939:56-57) states that rivers are not barriers to movement of pocket gophers where the river completely freezes over and has the ice covered with thick snow. Although the Jordan River does occasionally freeze over, it is never frozen for more than a few days at a time, and snow in this area does not last for long periods. The material at hand indicates that the gophers from both sides of the river are referable to the same subspeciesalbicaudatus. The animals from the east side of the river are in the aggregate of characters the most typical ofalbicaudatusof anyin the entire range. Those from the west side of the river, although definitely referable toalbicaudatusdo show some intergradation withThomomys bottae robustus, the subspecies to the west.
The specimens from Bauer, Tooele County, are relatively uniform in color, and are considerably lighter than topotypes ofalbicaudatus. Their upper parts vary from Sepia to Saccardo's Umber as compared with near (13''''n) Black of the topotypes. The sides and underparts are lighter, due primarily to much less black in the underfur. They average slightly longer in total length, but shorter in hind foot. All cranial measurements are slightly smaller than in topotypes ofalbicaudatus. The shape of the skull closely resembles that ofalbicaudatus, although the rostrum, nasals, upper incisors and posterior tongues of the premaxillae tend to be narrower. This narrowness indicates intergradation withThomomys bottae stansburyi, the race nearest to the west. These animals are in the majority of characters referable toalbicaudatus.
Bauer is situated in extreme western Tooele Valley at the foot of Stockton Bar, a low pass between the Stansbury and the Oquirrh mountains. This valley lies to the west of the aforementioned Jordan River. Although these gophers are definitely referable toalbicaudatusthey are more unlike topotypes than are the animals from Riverton.
The specimens from Settlement Canyon, Oquirrh Mountains, Tooele County, show the same characteristics as those from Bauer.
In a large series of animals from St. John, in Rush Valley, Tooele County, the upper parts vary from black, even darker than topotypes ofalbicaudatus, to Tawny Olive, and the underparts vary from black through Cinnamon Buff to Pinkish Buff. Most of the animals are Cinnamon Buff. Although variable they approachalbicaudatusin color. The total length, tail and hind foot of males are longer than in topotypes ofalbicaudatus; females differ in the same direction but only slightly. In both sexes the zygomatic breadth is less, but the mastoid breadth is greater than inalbicaudatus. In size and shape of the lacrimal processes, and the great thickening of the jugal at the maxillo-jugal suture they approachrobustus. They are much larger, however, and in the majority of characters are referable toalbicaudatus.
What has just been said relative to the animals from St. John applies also to those from Clover Creek in the Onaqui Mountains of Tooele County. At the latter locality the tendencies towardsrobustusare accentuated. This is to be expected, since this localityis midway between St. John and the type locality ofrobustus. All characters considered, these animals are all referable toalbicaudatus.
The animals from Little Valley, Sheeprock Mountains, Tooele County, resemblealbicaudatusin color. They vary on the upper parts from near (1) Sepia to Clay Color, and ventrally from nearly black to Pinkish Buff. They are markedly smaller in every measurement taken, except zygomatic and mastoidal breadths, and extension of premaxillae posterior to nasals. This relatively greater breadth indicates intergradation withrobustusto the west. These gophers are smaller in most measurements than any other population referred toalbicaudatus. This is understandable because gophers from mountains usually are smaller and have weaker, smoother skulls than animals from low lands. Although approachingrobustusin size and in some aforementioned cranial details, the aggregate of characters including color, make these animals referable toalbicaudatus.
The animals from Fairfield, Utah County, are closer geographically to the type locality ofalbicaudatusthan any other series, but morphologically are the least like topotypes. At first glance one is struck with the differences. They are uniformly Clay Color above, with Cinnamon Buff sides and flanks and Pinkish Buff underparts. Their color closely approaches that ofrobustusto the west which has Cinnamon Buff on the upper parts. Examination of eleven measurements of males and the same number for females, shows that the animals are nearest torobustusin two measurements, toalbicaudatusin 12, distinct in 7 and intermediate in one. The general appearance of the skull is intermediate between that of the two above mentioned forms. The differences fromalbicaudatusin size and color may be correlated with the differences in soil at Fairfield and Provo. At Fairfield the soil is light-colored clay, but at Provo it is sandy and darker. Although they are intergrades betweenrobustusandalbicaudatus, the animals are referred to the latter race. Utah Lake and its outlet, the Jordan River, make a partial barrier between populations at Fairfield and at the type locality at Provo. During Pleistocene times, when Lake Bonneville was present it formed a complete barrier. Enough time has evidently elapsed since the disappearance of this lake to allowalbicaudatus, the mainland form, to expand its range to the west. Intergradation has taken place, with the result that the animals from Fairfield, although unstable, agree with the mainland form,albicaudatus, in a majority of their characters.
Pocket gophers were taken at four localities from north to south in eastern Juab County. They range in color from Ochraceous Tawny on the upper parts and Cinnamon Buff on the underparts to shades that are slightly lighter. All are much lighter than topotypes ofalbicaudatus. The general configuration of the skull is the same as that ofalbicaudatus, and this is especially true in the females. In the narrower rostrum and weaker dentition they approachcontractus, but are distinctly lighter colored. Hall (1931:3) referred one specimen from Nephi, Juab County, toThomomys bottae aureiventris. Since that timeThomomys bottae leniswhich has some affinities withaureiventrishas been described (see account ofcontractus). The large series now available from Nephi and nearby localities do show some intergradation withlenis, in that four characters are more as inlenisandcontractusand seven characters are more as inalbicaudatus. Although differing markedly in many respects from topotypes ofalbicaudatusthey fit the aforementioned concept of this subspecies, and are being treated as a variable local population of it.
Provo is the locality listed for specimens which were available to naturalists from 1875-1877. To these specimens the following names were applied:Thomomys talpoides bulbivorusCoues (1875:256; 1877:627) andThomomys talpoides umbrinusCoues and Yarrow (1875:112). Possibly these names were applied to the animals currently known asThomomys bottae albicaudatuswhich does occur at Provo. Without the opportunity to examine the actual specimens, which so far as I know are no longer in existence, I cannot exclude the possibility that the locality designation "Provo" was used in a general sense to include pocket gophers taken a few miles to the eastward of Provo, where it is known that pocket gophers of only the speciesThomomys talpoides(current terminology) occur.
Specimens examined.—Total, 239, distributed as follows:Davis County: Bountiful, 4,500 ft., 1.Salt Lake County: Salt Lake City and environs, 4,300 ft., 51; 2 mi. W Murray, 4,300 ft., 6; Riverton, 4,300 ft., 11; Draper, 4,500 ft., 7; Rose Canyon, Oquirrh Mountains, 5,650 ft., 4.Tooele County: Bauer, 4,500 ft., 30; Settlement Creek, Oquirrh Mountains, 6,500 ft., 1; St. John, 4,300 ft., 28; Clover Creek, Onaqui Mountains, 5,500 ft., 15; Vernon, 4,300 ft., 2 (U. S. A. C.); Little Valley, Sheeprock Mountains, 5,500 ft., 20.Utah County: Fairfield, 4,800 ft., 24; Provo, 4,400 ft., 20 (8, B. Y. U.; 12, M. V. Z.).Juab County: Neff Farm, 4 mi. N Nephi, 5,000 ft., 2 (1, R. H.); Nephi, 5,000 ft., 1 (M. V. Z.); 2 mi. S Nephi, 4,700 ft., 14; 7 mi. SW Nephi, 6,000 ft., 2.
Specimens examined.—Total, 239, distributed as follows:Davis County: Bountiful, 4,500 ft., 1.Salt Lake County: Salt Lake City and environs, 4,300 ft., 51; 2 mi. W Murray, 4,300 ft., 6; Riverton, 4,300 ft., 11; Draper, 4,500 ft., 7; Rose Canyon, Oquirrh Mountains, 5,650 ft., 4.Tooele County: Bauer, 4,500 ft., 30; Settlement Creek, Oquirrh Mountains, 6,500 ft., 1; St. John, 4,300 ft., 28; Clover Creek, Onaqui Mountains, 5,500 ft., 15; Vernon, 4,300 ft., 2 (U. S. A. C.); Little Valley, Sheeprock Mountains, 5,500 ft., 20.Utah County: Fairfield, 4,800 ft., 24; Provo, 4,400 ft., 20 (8, B. Y. U.; 12, M. V. Z.).Juab County: Neff Farm, 4 mi. N Nephi, 5,000 ft., 2 (1, R. H.); Nephi, 5,000 ft., 1 (M. V. Z.); 2 mi. S Nephi, 4,700 ft., 14; 7 mi. SW Nephi, 6,000 ft., 2.
Type.—Male, adult, skin and skull, No. 3576, Museum of Zoölogy, University of Utah; Fish Springs, 4,400 ft., Juab County, Utah; June 8, 1940; collected by S. D. Durrant; original number 1955.
Range.—Known only from the type locality.
Diagnosis.—Size medium (see measurements); claws on front feet small. Color: Entire dorsal surface Warm Buff; sides near (e) Cinnamon Buff, underparts near (16") Pale Pinkish Buff; inguinal region, front and hind feet and distal part of tail white: top of head, nose and cheeks grayish black; postauricular patches small and grayish black; ears small, pointed and with heavily pigmented pinnae. Skull: Angular, short and wide; nasals of medium length, narrow proximally but widely flared distally; interparietal small; lambdoidal suture concave towards the interparietal; zygomatic arches uniformly widely spreading; interpterygoid space widely V-shaped; extension of premaxillae posterior to nasals long; lambdoidal crest well developed.
Comparisons.—From topotypes ofThomomys bottae aureiventris,bonnevilleidiffers as follows: Size smaller, hind foot shorter. Color: Upper parts and sides lighter; underparts pale buff rather than "gold." Skull: Shorter and relatively wider; rostrum wider and heavier; zygomatic arches relatively wider and more massive, with greatest width posteriorly instead of anteriorly; interpterygoid space widely V-shaped rather than lyre-shaped; thickening at union of jugal and zygomatic process of maxilla less developed; anterior palatine foramina larger; nasals shorter and more markedly flared distally; zygomatic breadth relatively, and mastoidal breadth actually, wider; extension of premaxillae posterior to nasals greater; tympanic bullae more inflated ventrally; upper incisors wider.
From near topotypes ofThomomys bottae centralis, from 1 mile east of Garrison, Millard County, Utah,bonnevilleidiffers as follows: Size smaller; hind foot and tail shorter. Color: Generally darker above and lighter below; top of head darker; postauricular patches smaller and lighter. Skull: Shorter and wider (zygomatic breadth expressed in percent of basilar length being, in males, 74.5 inbonnevilleiand 71.5 incentralis); interpterygoid space more widely V-shaped; interparietal smaller, and more triangular; nasals shorter and much more dilated distally, as well as more constricted proximally; lacrimal processes smaller and less globuse at tips; temporal fossae larger; braincase and entire dorsal surface of skull more nearly flat; lambdoidal suture convex posteriorly as opposed to nearly straight; tympanic bullae more inflated ventrally.
Comparisons ofbonnevilleiwith the type and type series ofThomomys bottae wahwahensisshow them to be of approximately the same size, but to differ as follows: Color: Slightly darker above and lighter below; postauricular patches smaller and lighter. Skull: Larger in every measurement taken, except breadth of rostrum which is smaller; skull not as flat; tympanic bullae more inflated ventrally; nasals and rostrum longer; extension of premaxillae posteriorto nasals greater; interparietal smaller and more triangular; zygomatic arches more bowed out laterally; jugals heavier; interpterygoid space more widely V-shaped; upper incisors less massive.
The characters that distinguishbonnevilleifromThomomys bottae albicaudatusare: Size smaller. Color: Markedly lighter throughout. Skull: Shorter and wider; mastoid and zygomatic breadths greater; rostrum narrower but shorter; angle between rostrum and zygomatic processes of maxillae less; interparietal smaller and more triangular; extension of premaxillae posterior to nasals greater; upper incisors shorter, narrower and more recurved.
T. b. bonnevilleiis indistinguishable in color fromThomomys bottae convexus, but differs from it in the following features: Size larger in nearly every measurement taken. Skull: Flattened dorsally as opposed to convex; zygomatic arches longer and weaker; jugals more nearly perpendicular; tympanic bullae larger; upper incisors longer; alveolar length of upper molar series the same, but molars narrower; rostrum longer but nasals shorter; extension of premaxillae posterior to nasals greater.
Topotypes ofbonnevilleican be distinguished from those of bothThomomys bottae tiviusandstansburyiby being larger in every measurement taken, by markedly lighter color throughout, and by ridged, massive, angular skulls rather than smooth, weak, nonangular skulls.
The races closest geographically tobonnevilleiareThomomys bottae robustusandT. b. sevieri. Compared with topotypes ofrobustus,bonnevilleidiffers in: Size larger. Color: Lighter throughout. Skull: Larger, although not as compact; zygomatic arches more widely spreading; jugals lighter; lacrimal processes not as prominent; zygomatic processes of maxillae not as robust; nasals more flared distally; extension of premaxillae posterior to nasals greater; alveolar length of upper molar series longer; molars larger; upper incisors longer, wider and darker in color; when placed ventral side down on a surface, the dorsal face of a skull ofrobustusis approximately parallel to the surface, whereas one ofbonnevilleidips down in the occipital region.
T. b. sevierican be easily distinguished frombonnevilleiby being smaller in every measurement taken, darker in color, and by small, weak, smooth skulls as opposed to large, robust, ridged skulls.
Remarks.—Fish Springs, wherebonnevilleioccurs is a marshy area south of the barren, salt-desert country of western Utah. The source of water is springs at the base of the north end of the FishSprings Mountains. Only the moist area supports pocket gophers. Specimens from Trout Creek, Juab County, twenty-five miles to the southwest are intergrades betweenbonnevilleiandaureiventris, and are referred to the latter subspecies. The country between Fish Springs and Trout Creek in 1937 and 1940 lacked pocket gophers; it was of the playa and sand type. ProbablyT. b. bonnevilleiwas derived fromT. b. aureiventris, a western mainland form of Pleistocene Lake Bonneville, through isolation and subsequent differentiation morphologically. The moist soils at Cane Springs, seven miles south of Fish Springs, had no pocket gophers when visited in 1940.
Specimens examined.—Total, 11, from the type locality.
Specimens examined.—Total, 11, from the type locality.
Thomomys perpallidus centralisHall, Univ. California Publ. Zoöl., 32:445, July 8, 1930.Thomomys bottae centralisGoldman, Proc. Biol. Soc. Washington, 48:156, October 31, 1935; Hall and Johnson, Proc. Utah Acad. Sci. Arts and Letters, 15:121, 1938.
Thomomys perpallidus centralisHall, Univ. California Publ. Zoöl., 32:445, July 8, 1930.
Thomomys bottae centralisGoldman, Proc. Biol. Soc. Washington, 48:156, October 31, 1935; Hall and Johnson, Proc. Utah Acad. Sci. Arts and Letters, 15:121, 1938.
Type.—Male, adult, skin and skull, No. 41688, Museum of Vertebrate Zoölogy, University of California; 2-1/2 mi. E Baker (1-1/4 mi. W Nevada-Utah boundary on 39th parallel), 5,700 ft., White Pine County, Nevada; May 30, 1929; collected by E. Raymond Hall; original number 2683.
Range.—Extreme western Utah, in Millard, Beaver and Iron counties.
Diagnosis.—Size medium (see measurements); tail long; claws on front feet long. Color: Near Cinnamon Buff on upper parts, darker in middorsal region, grading to Pinkish Buff on underparts, more accentuated in pectoral and inguinal regions; nose, cheeks and postauricular patches grayish black; front and hind feet and distal half of tail white. Skull: Robust and moderately ridged; zygomatic breadth about the same for entire length of arches; jugals vertical posterior to middle; moderate thickening present at region of maxillo-jugal suture; interpterygoid space narrowly V-shaped; dorsal frontomaxillary sutures convex medially; lacrimal processes globose and well developed; nasals long and with distal denticulations; paroccipital processes well developed.
Comparisons.—Compared with topotypes ofThomomys bottae albicaudatus,centralisdiffers as follows: Size larger; tail longer; claws on front feet longer. Color: Lighter throughout, Cinnamon Buff as opposed to near (13''''n) Black. Skull: Basilar length and length of nasals greater; zygomatic breadth less; zygomatic arches thicker at region of maxillo-jugal sutures; interpterygoid space more broadly V-shaped; dorsal frontomaxillary sutures convex medially as opposed to straight; paroccipital processes more developed; zygomatic arches approximately the same width throughout as opposed to widest posteriorly.
For comparisons withThomomys bottae aureiventrissee account of that form.
T. b. centraliscan be distinguished fromThomomys bottae bonnevillei,robustus,sevieriandconvexusby larger size throughout and generally darker color (see accounts of those forms). FromThomomys bottae stansburyiandtivius,centralisdiffers in larger size throughout and lighter color (see accounts of those forms).
Remarks.—Thomomys bottae centralishas one of the most extensive ranges of any of the known races ofT. bottae. The eastern limits extend into extreme western Utah. Specimens from Utah for the most part are intergrades betweencentralisandaureiventris, the race to the north. Some minor intergradation is also noted betweencentralisandsevieriandbonnevillei, the races to the east. Intergradation is the expected condition because the animals belonging tocentralisare at the extremes of their range in this area. The greater affinities of these animals withaureiventrisis to be expected because bothaureiventrisandcentralisare forms of the western mainland of the Pleistocene Lake Bonneville; while the races to the east, although closest geographically, were isolated from the gophers of the western mainland during prehistoric times by this lake. They are still isolated and enough time has elapsed so that only vestiges of morphological intergradation exist betweencentralisand these eastern forms. Two specimens from Cedar City, Iron County, are intergrades betweenThomomys bottae wahwahensis,centralisandplanirostris. Their skulls are slightly convex as inplanirostris, and the rostrum is short and wide as inwahwahensis. In shape of the zygomatic arches, length of the nasals, and color, they resemblecentralisto which they are here referred.