Zoogeographic Implications of Holocene Mammal Remains from Ancient Beaver Ponds in Oklahoma and New Mexico

Abstract

Some sediments exposed in cutbanks of streams in canyons in northeastern New Mexico and adjacent Oklahoma are considered to be filled-in beaver ponds and associated fringing meadows. Exposures rich in mollusk remains yielded small but important late Pleistocene and Holocene faunas. Five localities, approximately 31,000 to 500 YBP, were sampled. We present our hypothesis for the genesis of the valley fills, and discuss the zoogeographic significance of Thomomys bottae, Sigmodon hispidus, Microtus ochrogaster, and Microtus pennsylvanicus. The Cimarron River and its tributaries flow through the north-central corner of the Oklahoma Panhandle and adjacent parts of New Mexico. The river has cut through Tertiary basalts and Mesozoic strata (Schoff and Stovall, 1943) to form a rugged, dissected topography of mesas and can- yons. The land is semi-arid, and level areas sup- port short-grass prairie. Rough and broken land is clothed in juniper and Colorado pinyon (Pinus edulus).