Thomomys Wied-Neuwied, 1839 . Nova Acta Phys.-Med. Acad. Caes. Leop.-Carol., 19(1):377.

TYPE SPECIES: Thomomys rufescens Wied-Neuwied, 1939 (= T. talpoides rufescens).

SYNONYMS: Megascapheus Elliot, 1903 .

COMMENTS: Recent species allocated to two subgenera (Thaeler, 1980): Thomomys, which includes the species talpoides, clusius, idahoensis, mazama, and monticola; and Megascapheus including bottae, bulbivorus, townsendii, and umbrinus. Phylogenetic relationships among members of the subgenus Megascapheus were presented by Patton and Smith (1981), based on molecular data. Specific boundaries for some forms are poorly defined, but Patton and Smith (1989) provided an operational definition that can be applied to all pocket gophers.