Thomomys bottae centralis Goldman, Proc. Biol. Soc. Washington, 48:156, October 31, 1935; Hall and Johnson, Proc. Utah Acad. Sci. Arts and Letters, 15:121, 1938.
Type.—Male, adult, skin and skull, No. 41688, Museum of Vertebrate Zoölogy, University of California; 2-1/2 mi. E Baker (1-1/4 mi. W Nevada-Utah boundary on 39th parallel), 5,700 ft., White Pine County, Nevada; May 30, 1929; collected by E. Raymond Hall; original number 2683.
Range.—Extreme western Utah, in Millard, Beaver and Iron counties.
Diagnosis.—Size medium (see measurements); tail long; claws on front feet long. Color: Near Cinnamon Buff on upper parts, darker in middorsal region, grading to Pinkish Buff on underparts, more accentuated in pectoral and inguinal regions; nose, cheeks and postauricular patches grayish black; front and hind feet and distal half of tail white. Skull: Robust and moderately ridged; zygomatic breadth about the same for entire length of arches; jugals vertical posterior to middle; moderate thickening present at region of maxillo-jugal suture; interpterygoid space narrowly V-shaped; dorsal frontomaxillary sutures convex medially; lacrimal processes globose and well developed; nasals long and with distal denticulations; paroccipital processes well developed.
Comparisons.—Compared with topotypes of Thomomys bottae albicaudatus, centralis differs as follows: Size larger; tail longer; claws on front feet longer. Color: Lighter throughout, Cinnamon Buff as opposed to near (13''''n) Black. Skull: Basilar length and length of nasals greater; zygomatic breadth less; zygomatic arches thicker at region of maxillo-jugal sutures; interpterygoid space more broadly V-shaped; dorsal frontomaxillary sutures convex medially as opposed to straight; paroccipital processes more developed; zygomatic arches approximately the same width throughout as opposed to widest posteriorly.
For comparisons with Thomomys bottae aureiventris see account of that form.
T. b. centralis can be distinguished from Thomomys bottae bonnevillei, robustus, sevieri and convexus by larger size throughout and generally darker color (see accounts of those forms). From Thomomys bottae stansburyi and tivius, centralis differs in larger size throughout and lighter color (see accounts of those forms).
Remarks.—Thomomys bottae centralis has one of the most extensive ranges of any of the known races of T. bottae. The eastern limits extend into extreme western Utah. Specimens from Utah for the most part are intergrades between centralis and aureiventris, the race to the north. Some minor intergradation is also noted between centralis and sevieri and bonnevillei, the races to the east. Intergradation is the expected condition because the animals belonging to centralis are at the extremes of their range in this area. The greater affinities of these animals with aureiventris is to be expected because both aureiventris and centralis are forms of the western mainland of the Pleistocene Lake Bonneville; while the races to the east, although closest geographically, were isolated from the gophers of the western mainland during prehistoric times by this lake. They are still isolated and enough time has elapsed so that only vestiges of morphological intergradation exist between centralis and these eastern forms. Two specimens from Cedar City, Iron County, are intergrades between Thomomys bottae wahwahensis, centralis and planirostris. Their skulls are slightly convex as in planirostris, and the rostrum is short and wide as in wahwahensis. In shape of the zygomatic arches, length of the nasals, and color, they resemble centralis to which they are here referred.
Specimens examined.—Total, 49, distributed as follows: Millard County: 1 mi. SE Gandy, 5,000 ft., 15 (M. V. Z.); White Valley (Tule Spring), 60 mi. W Delta, 4, (3 in R. W. Fautin Vertebrate Collection); Robison Ranch, 5,300 ft., (on Hendry Creek) Simonsons Ranch, 4,596 ft., 2 (M. V. Z.); 1 mi. E Garrison, 5,000 ft., 21; 5 mi. S Garrison, 5,400 ft., 5 (M. V. Z.). Iron County: Cedar City, 2 (M. V. Z.).