Stephen David Durrant

“ Comparisons.—Topotypical specimens of stansburyi can be readily distinguished from those of Thomomys bottae centralis, aureiventris and albicaudatus by being smaller in every measurement taken, particularly those of the skull; the skull is weaker and smoother. In color stansburyi is like albicaudatus but is much darker throughout than aureiventris and centralis. ”

“ Insofar as we are aware, these occurrences are the first to be recorded from Utah, and extend the known range of this subspecies 150 miles northward.
The specimens from Washington County are paler than those from Garfield County, and this pallor indicates intergradation with the subspecies P. p. olivaceus. Of animals from the Aquarius Plateau, those from the eastern and southern localities are pale and have a marked suffusion of ochraceous in the upper parts, whereas those from the western and northern localities are extremely dark owing to a heavy suffusion of black in the upper parts. ”

“ Three specimens from the East Entrance, and three from near the east entrance to Zion National Park are much darker than topotypes of planirostris. All of these animals are in worn pelage, thus allowing a great amount of the black underfur to show, which gives a markedly darker color. The unworn hair is only slightly darker than that of the topotypes. The cranial details prove these animals to be intergrades between planirostris and trumbullensis. They resemble trumbullensis in size of tympanic bullae, extension of the premaxillae posterior to the nasals and shape of the nasals. ”

“ 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 to albicaudatus. ”

“ As may be seen on the distribution map, three different subspecies of Thomomys bottae occur in Washington County. Down the river, below St. George, the race virgineus inhabits the Virgin River Valley below the narrows of the Beaverdam Mountains. Because these narrows are filled with water from wall to wall during periods of high runoff, they form an effective barrier at present to migration of pocket gophers. The mountains to the north of St. George are inhabited by the dark form, birdseyei. The type locality of planirostris is on the middle reaches of the Virgin River, in Zion National Park. ”

“ Actual specimens were reported upon a year later by Elliot Coues (1875:251, 256) , who used the name Thomomys talpoides for specimens from "Utah" but later in the same paper listed specimens from Provo as Thomomys talpoides bulbivorus. Even as the great variation in Utah pocket gophers has been perplexing to modern workers, so it was also to Coues seventy years ago who left the problem with the statement that animals from Provo "exhibit among themselves such variations that their labelling becomes a matter of indifference"! ”

“ 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 of albicaudatus. The shape of the skull closely resembles that of albicaudatus, although the rostrum, nasals, upper incisors and posterior tongues of the premaxillae tend to be narrower. This narrowness indicates intergradation with Thomomys bottae stansburyi, the race nearest to the west. ”

“ 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. ”

“ The races nearest geographically to minimus are Thomomys bottae nesophilus and T. b. stansburyi. For comparisons see accounts of those forms.
Remarks.—This subspecies is the smallest of all the races of Thomomys bottae occurring 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 under nesophilus.) ”