Thomomys bottae stansburyi new subspecies
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 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.
Comparisons of topotypes of stansburyi with those of Thomomys bottae sevieri show 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 of Thomomys bottae minimus, stansburyi is 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 of Thomomys bottae, stansburyi most closely resembles tivius, a small, dark, mountain form from central Utah. Size and color are almost the same but stansburyi differs 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 Stansbury Mountains, by only a low pass. Pocket gophers from Clover Creek, Onaqui Mountains and Little Valley, Sheeprock Mountains, although intergrades between robustus and albicaudatus are dark in color like stansburyi. These intergrades are large, dark colored, and have heavy, ridged, angular skulls. It appears that stansburyi is a mountain subspecies derived from albicaudatus of the valley. It would be instructive to artificially transplant gophers from mountains to valleys, and vice 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.