Biocronología de roedores arvicólidos del Mioceno tardío al Pleistoceno de las Grandes Llanuras centrales de Norteamérica

Abstract

The Pliocene and Pleistocene record of arvicolid rodents from the central region of North America is broadly reviewed. A new provincial rodent zonation is proposed for the central Great Plains. Hemphillian arvicolids are represented by Promimomys and Protopliophenacomys. Although primitive species of Pliophenacomys are known from the early Blancan of Indiana and Kansas, this genus is conspicuously absent from most of the early and middle Blancan localities of the Meade Basin of Kansas. Advanced species of Pliophenacomys, with positive enamel differentiation, characterize late Blancan deposits, and appear to be good index fossils for this time period, especially in combination with advanced species of Ophiomys. Ogmodontomys poaphagus is the most common arvicolid through much of the Pliocene in Kansas and Nebraska. Bog lemmings are late Blancan immigrants to the central Great Plains. The disappearance of archaic arvicolids from the Borchers local fauna of Kansas at 2.10 Ma heralds the transition from the Blancan to Irvington-ian North American Land Mammal Age (NALMA). A Microtus immigration event characterizes the beginning of the Pleistocene and the Irvingtonian NALMA at Nash 72, Kansas. Early Irvingtonian deposits contain Microtus cf. pliocaenicus and Mictomys kansasensis, whereas later ones include a more advanced suite of arvicolids such as Microtus ochrogaster /llanensis, M. meadensis, M. paroperarius, and Mictomys meltoni. Exclusively modern arvicolids are recorded in latest Irvingtonian or earliest Rancholabrean deposits above the Lava Creek B ash (0.67 Ma), such as Butler Spring.