The entoptychine geomyid Lignimus hibbardi, sp. nov., is described from the WaKeeney local fauna, and the generic diagnosis is changed to include taxa with dentine tracts on cheek teeth, and with the X-pattern of lower molars not emphasized by a V-shaped ridge as in the type species, L. montis. Occlusal patterns of lower premolars and molars of Lignimus resemble those of entoptychines, and differ markedly from those of geomyines; hence the subfamilial reference. Lignimus cf. L. montis occurs in the Norden Bridge local fauna, and Lignimus sp. in the Norden Bridge local fauna and the Crookston Bridge and Burge Members of the Valentine Formation.

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