AN UNEXPECTED EARLY RECORD OF MICTOMYS VETUS (ARVICOLINAE, RODENTIA) FROM THE BLANCAN (PLIOCENE) GLENNS FERRY FORMATION, HAGERMAN FOSSIL BEDS NATIONAL MONUMENT, IDAHO

摘要: The cooling during the Pliocene that preceded major continental glaciation in North America is recorded by thick fluvial and lacustrine sequences at Hagerman Fossil Beds National Monument (HAFO) southcentral Idaho (McDonald et al., 1996). Fossiliferous beds HAFO occur within nearly 200 m of exposed Glenns Ferry Formation west Snake River. This formation extends from southwestern into easternmost Oregon (Malde Powers, 1962). contains hundreds localities are Blancan American Land Mammal Age. Collection specimens these since late 1920s has resulted large repositories fossils currently housed, part, United States Museum, University Michigan Museum Paleontology (UMMP), Natural History (IMNH); additionally, smaller collections were accumulated other museums Today paleontological resources stewarded Park Service. In spite extensive previous collections, significant new discoveries still being made HAFO. The described here first records Mictomys vetus (Wilson, 1933) HAFO. These also earliest anywhere impact previously proposed scenarios arvicoline biochronology (i.e., Repenning Grady, 1988; 1995; Fejfar Repenning, 1998). curated vertebrate paleontology collection IMNH Pocatello, Idaho. #### Abbreviations AC, anterior cap; BRA1 BRA2, buccal (=labial) reentrant angles 1 2; LaPW, labial primary wing; LiPW, lingual LRA1, LRA2, LRA3, 1, 2, 3; m1, lower molar; m3, third PL, posterior loop; T1, T2, T3, triangles 3. ### RodentiaBowdich, 1821 Muridae Illiger, 1811 Arvicolinae Gray, 1821 Mictomys Figures …