A rodent fauna from later Cenozoic beds of southwestern Idaho

Abstract

The late Pliocene or early Pleistocene continental deposits occurring in southwestern Idaho have yielded scattered fossil mammalian remains during the past forty years or more. However, with the exception of beaver material described as Castor accessor by O. P. Hay nothing has been recorded concerning the rodents from these beds. That a diversified assemblage of types occurs in these later Cenozoic sediments is clearly shown by collections procured in recent years in the course of palaeontological explorations along the Snake River near Grand View and Hagerman, Idaho. The westerly of the two principal localities in this region of Idaho is situated on the west side of the Snake River approximately thirteen miles northwest of the town of Grand View. This site was investigated by the California Institute of Technology. The Hagerman locality, where extensive excavations were conducted by the United States National Museum, is situated on the Snake River across from the town of Hagerman. In an airline, the distance between the localities at Grand View and Hagerman is approximately sixty miles. The United States National Museum has generously permitted me to borrow the rodent collections obtained by that institution at the Hagerman locality. The beaver remains were not included, since important studies of this group are being conducted elsewhere. The present paper embraces therefore a study of the rodent types now known from the Hagerman and Grand View localities, with the exception of the material noted above, and grateful acknowledgment is made here for opportunity to study the National Museum collections. Recent comparative material was loaned by the Division of Vertebrate Zoology, California Institute. The illustrations of the rodent material were prepared from photographic enlargements by John L. Ridgway. The author also wishes to thank Dr. Chester Stock for opportunity to study the California Institute collections and for supervision of the work, as well as for a critical reading of the manuscript.