Thomomys bottae virgineus Goldman
Thomomys bottae virgineus Goldman, Proc. Biol. Soc. Washington, 50:133, September 10, 1937.
Type.—Male, adult, skin and skull, No. 262016, U. S. National Museum (Biological Surveys Collection); Beaverdam Creek, near confluence with Virgin River, Littlefield, 1,500 ft., Mohave County, Arizona; October 16, 1936; collected by Luther C. Goldman; original number 67 (after Goldman, type not seen).
Range.—Extreme southwestern Utah, in Beaverdam Wash, Washington County, Utah.
Diagnosis.—Size medium (see measurements). Color: Upper parts Cinnamon Buff, finely mixed with black; sides and flanks Pinkish Buff; underparts Pale Pinkish Buff; front feet, hind feet, and distal part of tail white; nose, cheeks, chin and top of head grayish black. Skull: Robust, with moderately wide zygomatic arches; zygomatic processes of maxillae wide; zygomatic processes of squamosals long; jugals concave laterally, giving the zygomatic arches the appearance of double bowing; nasals long; extension of premaxillae posterior to nasals long; tympanic bullae well inflated ventrally; pterygoid hamulae heavy; interpterygoid space widely V-shaped; molariform teeth large.
Comparisons.—For comparisons of virgineus with Thomomys bottae planirostris and T. b. birdseyei see accounts under those forms.
Topotypical specimens of virgineus can be distinguished from those of Thomomys bottae trumbullensis as follows: Size smaller. Color: Lighter throughout. Skull: Zygomatic arches less widely spreading; jugals more bowed medially; zygomatic processes of squamosals longer; extension of premaxillae posterior to nasals greater; tympanic bullae larger and more inflated ventrally; molariform teeth larger.
Compared with topotypes of Thomomys bottae centralis, virgineus differs in: Size smaller; tail shorter; hind foot smaller. Color: Deeper Cinnamon Buff, thus darker in overall appearance. Skull: Smaller, but relatively wider; zygomatic processes of maxillae heavier; region of maxillo-jugal sutures thicker; jugals more concave laterally; tympanic bullae more inflated ventrally; molariform teeth larger.
Remarks.—This pocket gopher occupies practically the same range in Utah as the large kangaroo rat Dipodomys deserti deserti Stephens. Both are found in the Beaverdam Wash. The type locality of virgineus is but a short distance down the Beaverdam Creek at Littlefield, Arizona. It intergrades with birdseyei, the mountain form to the north and east (see remarks under birdseyei). There are evidences of intergradation with planirostris of the Virgin River Valley above the narrows of the Virgin River where it cuts through the Beaverdam Mountains (see the discussion under planirostris). There are intergradational tendencies exhibited towards centralis in some specimens. Some of the animals are practically indistinguishable in color and there are intergrading cranial characters in the nasals, zygomatic arches and tympanic bullae.
Specimens examined.—Total, 20, distributed as follows: Washington County: Beaverdam Wash, 8 mi. N Utah-Arizona border, 7; Beaverdam Wash, 5 mi. N Utah-Arizona border, 2,600 ft., 13.