The Pocket Gophers (Genus Thomomys) of Utah / University of Kansas Publications, Museum of Natural History, Vol. 1 No. 1

Thomomys talpoides ravus new subspecies

Type.—Male, adult, skin and skull, No. 13690, Carnegie Museum; Vernal-Manila Highway, 19 mi. N Vernal, 8,000 ft., Uintah County, Utah; August 22, 1937; collected by J. K. and M. T. Doutt; original number 4718.

Range.—Uinta Mountains in Daggett, northern Uintah and northern Summit counties.

Diagnosis.—Size large (see measurements); ears relatively narrow; hind foot relatively small. Color: Upper parts between Drab and Light Drab, darkest along middorsal line due to mixture of hairs tipped with light brown; sides and flanks Light Drab; entire underparts creamy white; front and hind feet, ventral surface of tail and end of tail white; proximal two-thirds of tail covered dorsally with light brown hairs; nose and cheeks dusky; postauricular patches black. Skull: Large, heavy and ridged; rostrum long and narrow; nasals long, moderately dilated distally and with a distal hump; posterior ends of nasals emarginate; parietal and lambdoidal crests well developed; zygomatic arches moderately heavy and widely spreading, widest posteriorly; zygomatic processes of maxillae moderately heavy and flaring abruptly from base of rostrum; marked middorsal depression in frontals present; interparietal pentagonal; extension of premaxillae posterior to nasals long; posterior tongues of premaxillae long, slender and rounded proximally; braincase high, vaulted and relatively narrow; tympanic bullae well inflated ventrally, and ridged in old animals; pterygoid hamulae long; interpterygoid space narrowly V-shaped; upper incisors long and narrow; molariform teeth medium.

Comparisons.—Compared with topotypes of Thomomys talpoides bridgeri, ravus differs as follows: Size larger; hind foot smaller; ears narrower. Color: Lighter throughout, grayish as opposed to brown. Skull: Smaller, narrower, less angular and less massive; nasals, rostrum, zygomatic processes of maxillae, ascending branches of premaxillae and posterior tongues of premaxillae all narrower; extension of premaxillae posterior to nasals longer; interparietal wider; braincase higher and narrower; tympanic bullae approximately the same size, but more inflated ventrally; interpterygoid space more narrowly V-shaped; upper incisors narrower; molariform teeth weaker.

Compared with topotypes and near topotypes of Thomomys talpoides uinta, ravus differs as follows: Size larger in every measurement taken. Color: Lighter throughout, being grayish as opposed to brown. Skull: Larger in every measurement taken; rostrum and nasals actually as well as relatively longer; extension of premaxillae posterior to nasals longer; upper incisors longer and wider; molariform teeth larger.

There is only one other gray subspecies of Thomomys talpoides in Utah, Thomomys talpoides ocius. Topotypes of ravus differ from it as follows: Size markedly larger in every measurement taken. Color: Darker, more brown hairs. Skull: Larger in every measurement taken; premaxillae extended farther posteriorly to nasals; extension of supraoccipital posterior to lambdoidal suture markedly less; tympanic bullae actually as well as relatively smaller; upper incisors longer and more procumbent.

This new subspecies can be readily distinguished from all other subspecies of Thomomys talpoides occurring in Utah by markedly greater size and paler, more grayish color.

Remarks.—The range of this form appears to be limited to the north slopes of the Uinta Mountains, except in Daggett County where it occurs also on the south slopes. Intergradation in color and in cranial details with bridgeri is shown by animals from the East Fork of Blacks Fork, thirty-one miles SSW Fort Bridger, and by those from Henrys Fork, 8,300 ft., both in Summit County. Due to the grayish color and the narrower, weaker skull they are referred to ravus. Intergradation with uinta is shown by specimens from the type locality of the latter race. The type series of uinta consists of intergrades between ravus and the animals to the west and south (see remarks under uinta).

It is doubtful whether bridgeri occurs in Utah. Material from Rich County and extreme northern Cache County would settle the question. Perhaps bridgeri is restricted to the lower valleys in southwestern Wyoming. Two specimens from northern Cache County, from Logan Canyon, Beaver Basin, Utah-Idaho Line appear to be intergrades between bridgeri and wasatchensis, but are referable to the latter race.

Thomomys talpoides ocius Merriam

Type.—Male, adult, skin and skull, No. 18852/25586, U. S. National Museum (Biological Surveys Collection); dry sagebrush mesas at Harveys Ranch, Smiths Fork, 6 mi. SW Fort Bridger, 6,657 ft., Uinta County, Wyoming; May 24, 1890; collected by Vernon Bailey; original number 1194 (after Bailey, type not seen).

Diagnosis.—Size small (see measurements). Color: Upper parts Tilleul Buff overlaid with Avellaneous, grading over sides and flanks to nearly white on underparts; underparts with faint wash of creamy white; postauricular patches small and dusky and completely circling the ear; nose and cheeks dusky; front feet, hind feet, throat, ventral surface of tail and distal half of tail white. Skull: Small, slender but compact; nasals rounded posteriorly; extension of premaxillae posterior to nasals very short; zygomatic arches robust, but not widely spreading, widest posteriorly; interparietal large and pentagonal in shape; extension of supraoccipital posterior to lambdoidal suture long; tympanic bullae actually as well as relatively large; basioccipital narrow; pterygoid hamulae long and ridged; upper incisors short and strongly recurved.

Comparisons.—Compared with one topotype and seven near topotypes of Thomomys talpoides pygmaeus, ocius differs as follows: Size larger in every measurement taken. Color: Lighter throughout, grayish as opposed to brown; distal half of tail white as opposed to only a few white hairs at tip of tail. Skull: Larger in every measurement taken; skull more compact; zygomatic arches heavier and more widely spreading posteriorly; tympanic bullae larger; upper incisors larger, but equally strongly recurved; molariform teeth larger.

Topotypes of ocius can be distinguished from those of Thomomys talpoides uinta as follows: Color: Lighter throughout, grayish as opposed to brown. Skull: Nasals rounded posteriorly as opposed to emarginate; zygomatic arches more robust; interparietal pentagonal as opposed to subquadrangular; extension of supraoccipital posterior to lambdoidal suture markedly greater; tympanic bullae actually as well as relatively much larger; upper incisors short and strongly recurved as opposed to long and procumbent.

Specimens of this subspecies can be distinguished from all other members of the species Thomomys talpoides occurring in Utah by their grayish color, and by small, compact skulls with very large tympanic bullae and short strongly recurved upper incisors.

Remarks.—Two specimens from Vernal, Uintah County, are intergrades between ocius and uinta. They resemble uinta in size and dorsal color, but are slightly lighter tending toward the color of ocius. Ventrally they are intermediate in color but more like ocius. The skulls are more like those of ocius in general appearance, extension of supraoccipital posterior to the lambdoidal suture, shape and thickness of the zygomatic arches, posterior tongues of premaxillae, size of tympanic bullae and recurved upper incisors. They more closely resemble uinta in shape of posterior ends of nasals, basioccipital and shape of the zygomatic processes of the squamosals. In all of the above mentioned characters, they are intermediate between the two named forms, but tend towards one or the other as listed. The majority of characters are more as in ocius to which they are here referred.

When Goldman (1939:233, 234) listed the named subspecies of Thomomys talpoides, he hesitated to include ocius and merely mentioned that ocius, pygmaeus and idahoensis might also belong to talpoides. Davis (1939:240, 241) found intergradation between idahoensis and fuscus and also between idahoensis and pygmaeus, and, therefore, arranged the last two mentioned forms as subspecies of talpoides. This present study reveals intergradation between ocius and uinta, and also between ocius and fossor (see account of fossor). Therefore, ocius is properly to be treated as a subspecies of the series of intergrading forms of which talpoides is the earliest named.

All specimens of ocius known from Utah are from the extreme eastern part of the northeastern corner of the state. The type locality of ocius is near Fort Bridger, Wyoming, which is north of Utah. I have seen one specimen from 12 miles west of Linwood, Daggett County, Utah, on Henrys Fork in Wyoming. Additional collecting in northern Utah probably will reveal ocius to inhabit also parts of northern Utah.

Thomomys talpoides moorei Goldman

Type.—Male, adult, skin and skull, No. 248222, U. S. National Museum (Biological Surveys Collection); 1 mi. S Fairview, 6,000 ft., Sanpete County, Utah; February 19, 1928; collected by A. W. Moore; X-catalogue number 24799 (after Goldman, type not seen).

Range.—Wasatch Plateau in Sanpete, Utah, Carbon and Emery counties, and in Wasatch Mountains south of Spanish Fork Canyon.

Diagnosis.—Size medium (see measurements). Color: Upper parts between Cinnamon and Sayal Brown, with mixture of black hairs, grading through Cinnamon on sides and flanks to Pale Pinkish Buff on underparts, clearest on inguinal and pectoral regions; nose and cheeks dusky; postauricular patches medium in size and black; ears black; chin buffy white; front and hind feet white; tail mostly white with brownish hairs on dorsal surface. Skull: Large, robust; nasals long and deeply emarginate on posterior ends, and dilated distally; zygomatic arches robust and widely spreading; zygomatic processes of maxillae heavy; interparietal comparatively small, but always wider than long; extension of premaxillae posterior to nasals short; tympanic bullae moderate in size, but markedly inflated ventrally; pterygoid hamulae long; interpterygoid space narrowly V-shaped; upper incisors long and moderately recurved; molariform teeth light.

Comparisons.—Topotypes of moorei differ from topotypes and near topotypes of Thomomys talpoides uinta as follows: Size slightly larger. Color: Upper parts and sides lighter; tail lighter; postauricular patches larger and darker; ears more pointed, smaller and darker. Skull: Larger, heavier and more massive; nasals longer, but deeply emarginate posteriorly as in uinta; rostrum wider and longer; zygomatic arches heavier and more angular; zygomatic processes of maxillae heavier; interparietal generally smaller and shorter; braincase wider; tympanic bullae more inflated ventrally; interpterygoid space more narrowly V-shaped; upper incisors longer, but not as procumbent; molariform teeth smaller.

Topotypes of moorei can be distinguished from those of Thomomys talpoides oquirrhensis as follows: Size slightly larger; tail longer; ears larger, less pointed. Color: Lighter throughout; postauricular patches larger. Skull: More ridged and angular; nasals narrower posteriorly, but more dilated distally; posterior ends of nasals more deeply emarginate (while shallowly emarginate in oquirrhensis, they tend to be somewhat rounded); rostrum narrower; extension of premaxillae posterior to nasals greater; least interorbital breadth less; zygomatic arches more angular and widely spreading; zygomatic processes of maxillae heavier; interparietal smaller; tympanic bullae larger and more inflated ventrally; upper incisors generally longer.

The characters that distinguish moorei from Thomomys talpoides parowanensis are: Color: Lighter throughout. Skull: Broader, more angular and more nearly flat; zygomatic arches more widely spreading; zygomatic processes of maxillae heavier; posterior ends of nasals emarginate rather than rounded; upper incisors longer.

For comparisons of moorei with Thomomys talpoides levis and wasatchensis see accounts of these forms.

Remarks.—Specimens from Colton, show intergradation between moorei, uinta and wasatchensis, but are referable to moorei in the majority of characters. Specimens from Mount Nebo, and the mouth of Reddicks Canyon, in the Wasatch and San Pitch mountains, respectively, are intergrades between moorei and wasatchensis, but are referable to moorei.

That part of the Wasatch Mountains south of Spanish Fork Canyon is inhabited by pocket gophers that are intergrades between moorei and wasatchensis, but the cranial details show them to be referable to moorei. The range here ascribed to moorei consists of the Wasatch Plateau to the east of Sanpete Valley, the San Pitch Mountains and the southern part of the Wasatch Mountains. The type locality of moorei is situated in the southern end of a high valley that separates the Wasatch Plateau from the San Pitch and Wasatch mountains. Topotypical animals are larger and have more ridged, angular skulls than those from the mountains.

Thomomys talpoides fossor Allen

Type.—Male, adult, skin and skull, No. 5240/4120, American Museum of Natural History; Florida, 7,200 ft., La Plata County, Colorado; June 25, 1892; collected by Charles P. Rowley (after Allen, type not seen).

Range.—In the mountains of San Juan and Grand counties, east of the Colorado and Green rivers.

Diagnosis.—Size medium (see measurements). Color: Upper parts Dresden Brown, grading over sides to Pale Buff on underparts; chin white; ears small, pointed, with deeply pigmented pinnae; postauricular patches grayish black; nose dusky. Skull: Long and narrow; nasals long, rounded proximally and usually simple distally; rostrum long; interparietal triangular; tympanic bullae large, and well inflated ventrally; basioccipital narrow; palate narrow; palatal pits shallow; dentition light.

Comparisons.—Near topotypes of fossor can be distinguished from topotypes of Thomomys talpoides ocius as follows: Size larger throughout. Color: Darker throughout, being dark brown as opposed to grayish. Skull: Longer and narrower; nasals and rostrum longer; extension of supraoccipital posterior to lambdoidal suture markedly less; tympanic bullae markedly smaller; upper incisors longer and not as strongly recurved.

Among the races of Thomomys talpoides occurring in Utah, fossor most closely resembles Thomomys talpoides uinta in color and size, but differs from it as follows: Ears smaller, more pointed and with more darkly pigmented pinnae. Skull: Longer, narrower and weaker; rostrum longer; nasals longer, and rounded proximally as opposed to markedly emarginate; interparietal triangular instead of roughly pentagonal; tympanic bullae larger and more inflated ventrally; basioccipital narrower; palate narrower, palatal pits shallower; dentition lighter.

Remarks.—Bailey (1915:111) remarked that fossor was one form that held its distinctive characters over a wide range. At that time, its range was understood to include practically all of the mountainous parts of Colorado, Utah as far west as the central part of the state, and parts of New Mexico, Arizona and Wyoming. Subsequently three new forms have been named from central Utah, (Goldman 1938:334-337) thereby showing variation to be much more prevalent than formerly supposed. The range of fossor in Utah, as now understood, is limited to the mountainous parts of the state south and east of the Colorado and Green rivers in Grand and San Juan counties.

The Utah specimens are not typical. At first glance some differences are noted in the premaxillae and nasals. Four specimens in the collections of the Museum of Natural History, University of Kansas, three from 3 miles east of Creede, Mineral County, and one from 10 miles east of Lake City, Hinsdale County, Colorado, both of which lie north and east of the type locality of fossor show the same characters as the Utah specimens.

Eight specimens from Oak Spring are intergrades between fossor and ocius. In size and color they are like fossor, but the skulls are intermediate. Because the animals are more like fossor in the majority of characters, they are here referred to that race.

As a result of these studies and due to the paucity of specimens from Utah, it is advisable, for the present, to refer all these Utah animals to fossor. Additional specimens may reveal characters that will merit the separation of the Utah animals from typical fossor; a desertlike area unfavorable to Thomomys exists between the type locality and eastern Utah.

Thomomys talpoides parowanensis Goldman

Type.—Male, adult, skin and skull, No. 158072, U. S. National Museum (Biological Surveys Collection); Brian Head, Parowan Mountains, 11,000 ft., Iron County, Utah; September 8, 1908; collected by W. H. Osgood; original number 3483 (after Goldman, type not seen).

Range.—High mountains of eastern Iron and Beaver counties, and western Kane and Garfield counties.

Diagnosis.—Size medium (see measurements). Color: Upper parts Sayal Brown moderately mixed with black, lightest on head; sides lightly washed with Buff; underparts Pinkish Buff, clearest on inguinal and pectoral regions; nose and cheeks dusky; postauricular patches large and black; front feet, hind feet and distal half of tail white. Skull: Long and fairly slender; zygomatic arches not widely spreading; nasals long; rostrum long and slender; posterior ends of nasals truncate or moderately emarginate; extension of premaxillae posterior to nasals usually short; tympanic bullae relatively small; upper incisors long and narrow; molariform teeth large.

Comparisons.—Compared with Thomomys talpoides kaibabensis, parowanensis differs as follows: Size smaller. Skull: Shorter; nasals shorter; zygomatic breadth less; nasals truncate or shallowly emarginate posteriorly as opposed to rounded; upper incisors narrower.

Topotypes of parowanensis differ from topotypes and near topotypes of Thomomys talpoides uinta as follows: Size larger. Color: Usually lighter; postauricular patches larger and darker; ears small with pinnae deeply pigmented as opposed to large and lightly pigmented. Skull: Larger; zygomatic arches more widely spreading; nasals longer; rostrum longer; posterior ends of nasals truncate or shallowly emarginate as opposed to deeply emarginate; sides of zygomatic arches nearly parallel and not so divergent posteriorly; interparietal larger and less quadrangular; extension of premaxillae posterior to nasals less; upper incisors less procumbent; molariform teeth larger.

Among named races of Thomomys talpoides, parowanensis most closely resembles levis, the race nearest geographically to the east, but differs from levis as follows: Size larger. Skull: Longer and wider; rostrum and nasals longer; interparietal quadrangular as opposed to roughly elliptical; upper incisors longer.

For comparisons with Thomomys talpoides moorei and wasatchensis see accounts of those forms.

Remarks.—The mountains of south central Utah are inhabited by pocket gophers that have been designated as Thomomys talpoides parowanensis and T. t. levis by Goldman (1938:334, 336). They are nearly indistinguishable in color and each is variable in cranial details. The diagnostic characters of each form occasionally appear, in varying degrees, throughout the range of the other. The Sevier River Valley separates the ranges ascribed to these two forms. This valley is inhabited by pocket gophers that belong to a different species, Thomomys bottae. The ranges of these two races of talpoides converge southward at the headwaters of the Sevier River. Specimens of parowanensis from the northern limits of its range from the Beaver Mountains in eastern Beaver County and those of levis from the northern limits of its range in the Fish Lake Mountains are readily distinguishable from each other. As the ranges converge to the southward, there is progressively more intergradation. The type locality of parowanensis is located in the southern part of its range, while that of levis is in the extreme northern part of its range. Therefore, due to the convergence of the two ranges at the south, the specimens from localities near the type locality of parowanensis show the greatest amount of intergradation, if we regard specimens of parowanensis from the type locality as typical of the race. Four specimens from Webster Flat, sixteen miles east of Cedar City, Iron County, and three from Duck Creek, Cedar Mountains, Kane County could equally well be assigned to either levis or parowanensis.

Thomomys talpoides levis Goldman

Type.—Female, adult, skin and skull, No. 158079, U. S. National Museum (Biological Surveys Collection); Seven Mile Flat, 5 mi. N Fish Lake, Fish Lake Plateau, 10,000 ft., Sevier County, Utah; October 1, 1908; collected by W. H. Osgood; original number 3616 (after Goldman, type not seen).

Range.—Fish Lake Mountains in Sevier County south into Garfield County, Utah.

Diagnosis.—Size medium (see measurements). Color: Upper parts near Sayal Brown, moderately mixed with black, darkest on head and middorsal region, grading to Cinnamon Buff on sides and flanks; underparts Pinkish Buff, clearest on inguinal and pectoral regions; chin, cheeks and nose dusky; postauricular patches large and black; front feet, hind feet and distal half of tail white; ears small and deeply pigmented. Skull: Slender and weak; zygomatic arches not widely spreading; posterior ends of nasals rounded; nasals moderately long and narrow; rostrum long and narrow; extension of premaxillae posterior to nasals short; interparietal usually much wider than long; pterygoid hamulae ridged; interpterygoid space usually narrowly V-shaped; upper incisors short.

Comparisons.—Compared with topotypes of Thomomys talpoides moorei, levis differs as follows: Size smaller; tail shorter. Color: Darker throughout, especially on dorsal surface due to more black of the underfur; underparts deeper buff. Skull: Narrower, less massive; zygomatic processes of maxillae weaker and not as widely spreading; interparietal generally wider; extension of premaxillae posterior to nasals less; posterior ends of nasals rounded rather than emarginate; upper incisors shorter, less procumbent.

Topotypes of levis differ from near topotypes of Thomomys talpoides uinta as follows: Size larger. Color: Upper parts slightly darker; postauricular patches much darker and larger; ears small and deeply pigmented as opposed to large and lightly pigmented; tail darker all around at base, with white part more extensive and with fewer buff-colored hairs. Skull: More convex dorsally; zygomatic arches more widely spreading and angular; nasals longer; rostrum longer; interparietal wider and more elliptical; posterior ends of nasals rounded as opposed to emarginate; extension of premaxillae posterior to nasals less; pterygoid hamulae more ridged; interpterygoid space more narrowly V-shaped; upper incisors shorter and less procumbent.

Topotypes of levis can be distinguished from those of Thomomys talpoides kaibabensis by markedly smaller measurements.

For comparisons with Thomomys talpoides parowanensis and wasatchensis see accounts of those forms.

Remarks.—Specimens from the Escalante Mountains and the Aquarius Plateau are not typical. They are of approximately the same color as levis, but are larger than levis and have cranial details that indicate intergradation with kaibabensis to the south. They resemble kaibabensis in large size, long nasals and widely spreading zygomatic arches, but are like levis in shape of the interparietal, extension of premaxillae posterior to the nasals, rounded posterior ends of nasals, ridged pterygoid hamulae and relatively short upper incisors. Additional material from these regions may prove these animals to merit separation and naming.

Measurements of Adult Males of Thomomys

(In millimeters)

Measurements of Adult Females of Thomomys

(In millimeters)

Thomomys bottae (Eydoux and Gervais)

Thomomys bottae is a southern species that, within the Great Basin, reaches the most northern limits of its distribution in Utah. The animals of this species inhabit the lower valleys, and with the exception of the Oquirrh Mountains, inhabit also the mountains in that part of the state west of the central mountain ranges. The specific characters are: Sphenorbital fissure present; incisive foramina posterior to infraorbital canal; anterior prism of P4 rounded; interparietal relatively small; lambdoidal suture straight in region of interparietal, in Utah specimens.

Thomomys bottae aureiventris Hall