Five million years of pocket gopher history in the Meade Basin of southwestern Kansas and northwestern Oklahoma

ABSTRACT

The Meade Basin record of pocket gophers extends from the latest Miocene (Buis Ranch local fauna) to modern time. A primitive species with hypsodont but rooted cheek teeth, Pliogeomys buisi, characterizes the late Hemphillian. Another species of Pliogeomys, P. louderbachi, is described here as a new species from the early Blancan. It is intermediate in dental and mandibular morphology between Pliogeomys and Geomys. The Geomys minor (= G. smithi) lineage displays a stepped dwarfing trend prior to its extinction, whereas the G. jacobi lineage demonstrates an overall pattern of stasis in size. G. jacobi is replaced by G. quinni at the end of the Pliocene, within which there is a significant directional size increase. A late Pliocene immigrant, the new species G. floralindae, appears in the Sanders assemblage. It is briefly replaced by an indeterminate small species in the Nash 72 local fauna. G. tobinensis is found in the Cudahy local fauna. Morphologically modern G. bursarius appears in the Meade Basin during the early Rancholabrean. A small, primitive species, Geomys adamsi, appears only during the early Pliocene at Fox Canyon, and transient Thomomys appear at various times during the Pleistocene, both apparently during cold intervals. A phylogenetic analysis suggests two clades, one uniting Pliogeomys russelli and Geomys adamsi and another including the remaining Meade Basin geomyines. Enhanced species turnover and the last push for modern mandibular morphology is most pronounced in sediments younger than about 2.6 million years ago, corresponding to the first global cooling heralding the Pleistocene.

ACKOWLEDGMENTS

We appreciate the loan of material by G. Gunnell and P. Gingerich at the Museum of Paleontology, University of Michigan, and by N. Czaplewski, University of Oklahoma. L. D. Martin kindly allowed study of specimens at the Museum of Natural History, University of Kansas. We thank C. Mecklin, Department of Mathematics and Statistics at Murray State University, for help with statistical analysis. This research was funded by grants from the National Geographic Society (5963-97, 6547-99) and the National Science Foundation (EAR 0207582) and the Spanish Ministerio de Ciencia e Innovación (projects CGL2004-02094/BTE and CGL2008-04200/BTE). F. Marcolini was supported by a Marie Curie Fellowship (MC-OIF-CT-2005-008522).

paraHandling editor: Anjali Goswami