Thomomys fossor Bailey, N. Amer. Fauna, 39:112, November 15, 1915; Barnes, Bull. Univ. Utah, 12 (No. 15):85, April, 1922; Bull. Univ. Utah, 17 (No. 12):102, June, 1927; Hall, Univ. California Publ. Zoöl., 37:4, April 10, 1931; Presnall, Zion-Bryce Mus. Bull., 2:14, January, 1938; Tanner, Great Basin Nat., 1:111, 1940.
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.
Specimens examined.—Total, 24, distributed as follows: Beaver County: Britts Meadows, Beaver Mountains, 8,500 ft., 7 (3, M. V. Z.; 2, U. S. N. M.; 2, C. M.); Puffer Lake, Beaver Mountains, 1 (U. S. N. M.); Kents Lake, Beaver Mountains, 1 (R. H.). Iron County: Lava Beds, 3-1/2 mi. SW Panquitch Lake, 1 (C. M.); Brian Head, Parowan Mountains, 2 (1, U. S. N. M.; 1, C. M.); Webster Flat, 16 mi. E Cedar City, 4; Bear Valley, 2 mi. E B. V. Ranger Station, 1 (R. H.). Garfield County: 1/4 mi. W Sunset Point, Bryce National Park, 8,000 ft., 1 (M. V. Z.). Kane County: Navajo Lake, 3 (R. H.); Duck Creek, Cedar Mountains, 9,000 ft., 3 (1, R. H.).