Small Mammal Fossils and Correlation of Continental Deposits, Safford and Duncan Basins, Arizona, USA

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Fossil bearing continental deposits, the Gila Conglomerate, of Safford and Duncan Basins, Arizona were correlated with the magnetic polarity time scale by means of magnetostratigraphy and biochronology of mammalian fossils. Within the Safford Basin, the Bear Springs section with a middle Blancan fauna is correlated with the lower or upper Gauss chron; the 111 Ranch section with a middle to late Blancan fauna is correlated with the upper Gauss to early Matuyama chrons; and the San Simon Power Line section with probably a latest Blancan fauna is correlated with the early Matuyama chron. In the Duncan Basin, the Duncan section with a middle Blancan fauna is correlated with the middle Gauss chron; the Pearson Mesa section with a middle Blancan fauna is correlated with the upper Gauss chron; and the Country Club section with a middle Blancan fauna is correlated with the lastest Gilbert to early Gauss chrons or from the middle Gauss to the earliest Matuyama chrons. A late Blancan fauna is not recognized in the Duncan Basin at least within the study area, whereas the Gila Conglomerate in the Safford Basin includes deposits and fauna of the latest Blancan (latest Pliocene) age. A minimum of 37 taxa of small mammals are recognized among the approximately 1,600 specimens from the Gila Conglomerate of the Safford and Duncan Basins. In the Safford Basin, a minimum of 26 small mammal taxa are now recognized in the 111 Ranch fauna, of which three genera (Dipodomys, Peromyscus, and Repomys) are new records to the fauna; a minimum of 6 taxa of small mammals are recognized and described for the first time in the San Simon Power Line fauna. In the Duncan Basin, a minimum of 15 small mammal taxa are recognized and described for the first time. Three new rodent species are described. Pappogeomys (Cratogeomys) sansimonensis, n. sp. is characterized mainly by P^4 with or without narrow enamel plate posterolingually and M^<1-2> with narrow enamel plates posterolabially, representing more primitive condition of the subgenus. Reithrodontomys galushai, n. sp. is characterized by M^1 with the single cusped anterocone and weakly developed mesoloph, M_1 anteroconid indistinctly bilobed, and M_3 with an S-shaped occlusal pattern, representing a primitive form of fulvescens species group. Repomys arizonensis, n. sp. is characterized by its intermediate position in size and in certain dental characters between R. panacaensis and R. gustelyi, but is probably representing a different lineage. New combination of genus and species, Hypolagus virginiae, is described, representing the general similarity of P_3 pattern with the genus Aluralagus being a convergence.
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Small Mammal Fossils and Correlation of Continental Deposits, Safford and Duncan Basins, Arizona, USA

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