Ten species of geomyoid rodents are recognized from the early-early Arikareean Ridgeview local fauna of Nebraska: three heliscomyids, four florentiamyids, one heteromyid, and two species of the probable geomyid Tenudomys Rensberger, 1973. Two new genera are described, the heliscomyid Tylionomys and a harrymyine heteromyid Proharrymys. Two previously described Arikareean species are referred to Proharrymys: Heliscomys schlaikjeri Black, 1961 and Proheteromys fedti Macdonald, 1963 (new combinations). Four new species are named: the heliscomyids Heliscomys macdonaldi and Tylionomys voorheisi, the heteromyid Proharrymys wahlerti, and the probable geomyid Tenudomys ridgeviewensis.
Heliscomyids are more diverse in the Ridgeview local fauna than in any other Arikareean fauna in North America. This increases the known diversity of this family during a time interval from which only a single species was previously recognized. Larger florentiamyids are poorly represented in the fauna, but the sample is large enough to demonstrate that Florentiamys kennethi Wahlert, 1983 is a junior synonym of F. tiptoni (Macdonald, 1970). A large sample of the small florentiamyid Kirkomys Wahlert, 1984 is sufficient to demonstrate that Proheteromys nebraskensis Wood, 1937 is synonymous with Kirkomys milleri Wahlert, 1984, resulting in the new combination Kirkomys nebraskensis.
The only heteromyid in the fauna, P. wahlerti, is believed to be the basal harrymyine from which the Hemingfordian Harrymys can be derived.