Rodents of the Bridgerian (Middle Eocene) Elderberry Canyon Local Fauna of Eastern Nevada

Abstract

The Elderberry Canyon Local Fauna, presently represented by more than 40 vertebrate taxa, including at least 30 mammals, occurs in carbonate rocks assigned to the Sheep Pass Formation, near Ely, Nevada. Among the mammals, nine rodent species, representing four families, are recognized. <i>Reithroparamys delicatissimus</i>, and <i>R.</i> cf. <i>R. huerfanensis</i> are species previously known from the Rocky Mountain region; <i>Microparamys sambucus</i> and <i>Pauromys exallos</i> are new species assigned to genera commonly occurring in Eocene faunas elsewhere; <i>Elymys complexus</i> is a new genus and species of minute rodent thought to be related to <i>Simimys</i> and questionably assigned to the family Zapodidae; <i>Sciuravus, Mattimys</i>, and <i>Knightomys</i> are represented by material not assignable to species; and another unidentified ischyromyid completes the roster of rodents presently known in the assemblage. The fauna as a whole, and the rodents in particular, share the greatest homotaxial similarity with early Bridgerian (early middle Eocene) faunas elsewhere, allowing a confident early Bridgerian age assignment for the Elderberry Canyon Local Fauna. The composition of this rodent assemblage suggests that faunal interchange was relatively unrestricted from southern California through Nevada to the Rocky Mountain region in Bridgerian time.