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Two species of pocket gophers of the genus Thomomys (Family Geomyidae) occur in Colorado, Thomomys bottae (see fig. 1) in the low valleys in the south-central and southwestern parts of the state and Thomomys talpoides mainly in the mountains and high valleys. Thomomys bottae occurs primarily in the Piñon-juniper, Ponderosa Pine, and Short Grass zones of Daubenmire (1943) but in some localities is found in the Douglas Fir Zone. Thomomys talpoides occupies primarily the Douglas Fir Zone and Engelm

Adults of approximately equal age were compared in the study of geographic variation. Three criteria of adulthood are: (a) suture obliterated between supraoccipital and exoccipital, (b) suture at least partly obliterated between basisphenoid and basioccipital, (c) supraorbital crests not widely separated and almost parallel. In males the crests encroach on the lateral borders of the interparietal; in females the crests approach the lateral borders of the interparietal but are more widely separat

Thomomys bottae occurs in the Colorado Plateau Province (terminology of Fenneman, 1931), the Southern Rocky Mountain Province and a small part of the Great Plains Province. The Colorado Plateau Province, in the southwestern part of the state, is mostly above 5000 feet and is characterized by the great number of canyons cut by rivers and streams in the nearly horizontal strata. Prominent features of the landscape are cuestas, such as Mesa Verde, and laccoliths, such as Ute Peak. The Southern Rock

Six subspecies of Thomomys bottae occur in Colorado. T. b. aureus and T. b. howelli occupy the Colorado Plateau Province (see fig. 1) and are characterized by a yellowish color; nasals posteriorly truncate or rounded; posterior extensions of premaxillae long; basioccipital wide; and interpterygoid space U-shaped with a median spicule. T. b. internatus , T. b. cultellus , and a new subspecies from the vicinity of Cañon City described on page 376, inhabit the Sangre De Cristo and Wet mountains in

A study of 249 specimens of Thomomys bottae from Colorado reveals six subspecies in the state. T. b. aureus and T. b. howelli occupy the Colorado Plateau Region in the western and southwestern parts of the state. T. b. internatus , T. b. cultellus , T. b. pervagus , and the newly named T. b. rubidus occupy part of the Southern Rocky Mountain Region and a narrow strip of the Great Plains. The greatest amount of geographic variation, in Thomomys bottae in Colorado, occurs in the ecotone between th

Bailey, V. 1910. Two new pocket gophers of the genus Thomomys . Proc. Biol. Soc. Washington, 23:79-80, May 4. 1915. Revision of the pocket gophers of the genus Thomomys. U. S. Dept. Agric., Bur. Biol. Surv., N. Amer. Fauna, 39:1-136, 8 pls., 10 figs, in text, November 15. Daubenmire, R. F. 1943. Vegetational zonation in the Rocky Mountains. Bot. Rev., 9:325-393, June. Durrant, S. D. 1952. Mammals of Utah. Univ. Kansas Publ., Mus. Nat. Hist., 6:1-549, 91 figs. August 10. Fenneman, N. M. 1931. Phy