Morphometrics, schmelzmuster, and biogeography of selected late Quaternary small mammals from eastern North America with emphasis on the Wapsipinicon Local Fauna, Jones County, Iowa

Interpretations of paleoecology, fossil history and/or evolutionary relationships are primarily based on direct knowledge of living taxa, particularly during the Quaternary. Consequently, conclusions are heavily influenced by specific identification of fossil remains. This study tests the application of morphometric and schmelzmuster analysis against classic taxonomy for identifying small mammals from Quaternary fossil and archaeological micromammal assemblages.; Morphometric analysis of landmark data is used extensively by both invertebrate and vertebrate paleontologists to quantify morphology. Except for a few instances, however, morphometric identification of micromammals has not been developed. Herein, a landmark scheme for recording occlusal variation on the lower first molars of Microtus (Rodentia) is introduced and applied to fossils from the Jones Local Fauna (Kansas), Schmidt Local Fauna (Nebraska), and Wapsipinicon Local Fauna (Iowa). Using samples from living populations to establish discriminant standards, specific classification was greatly enhanced at all three sites and previously unrecognized taxa were identified in the Jones and Wapsipinicon local faunas.; Schmelzmuster (enamel microstructure) analysis is commonly used for biochronology, evolutionary dynamics, functional morphology, and phylogeny. Although largely utilized in Europe, the technique is tested here on samples from modern populations of six North American species of Microtus (M. chrotorrhinus, M. longicaudus, M. montanus, M. pennsylvanicus, M. ochrogaster, and M. pinetorum) for purposes of specific separation and/or distinction, and is applied to fossils from the Wapsipinicon Local Fauna. Results of the schmelzmuster analysis support identifications based on morphometrics.; The Wapsipinicon Local Fauna, which consists of two contemporaneous faunules recovered from Dutch Creek and Empty fissures, contains at least 44 mammalian taxa. Abundant taxa include three tundra indicators (Dicrostonyx torquatus, Lemmus sibiricus, and Microtus miurus), four steppe indicators (Geomys bursarius, Microtus ochrogaster, Spermophilus tridecemlineatus, and Thomomys talpoides), four eastern deciduous forest indicators (M. pinetorum, Scalopus aquaticus, Blarina cf. B. brevicauda, and Sciurus sp.) and eight boreal forest indicators (Clethrionomys sp., M. xanthognathus, M. pennsylvanicus, Phenacomys intermedius, Synaptomys borealis, S. cooperi, Eutamias minimus, and Tamiasciurus hudsonicus ). Although there has been some intrusion of postglacial taxa, the northern affinities of the most abundant taxa suggest that the assemblage is late Wisconsinan. Radiocarbon dates between 13,460 ± 120 and 25,470 ± 350 yr B.P. support this hypothesis.