First record of the archaic Eurasian cricetid rodent Microtodon from North America

A new species of the archaic arvicoline-like cricetid rodent Microtodon is described from the Hoye Canyon Local Fauna (LF), Douglas County, Nevada, U.S.A. This occurrence represents the first record of Microtodon and only the second record of ancient arvicolid-like cricetids from North America. The first, Ellesmereomys haringtoni, was described from the Strathcona locality, Canadian Arctic, about 4.0 Ma. The new Microtodon is characterised by a short anteroconid complex, shallow fourth lingual re-entrant angle (LRA4), and narrow anteroconid width on the first lower molar (m1). The new species resembles other Microtodon species and differs from Baranomys and all Promimomys species by lacking LRA1 on m3. Based on biostratigraphic correlations, the Hoye Canon LF was deposited about 5.8-5.6 Ma, roughly at the same time as the first Promimomys, P. mimus from the McKay Reservoir assemblage of Oregon, entered North America. Neither the Hoye Microtodon nor Ellesmereomys haringtoni are likely ancestral to Promimomys, but the two arvicoline-like cricetids attest to a previously unknown late Miocene - early Pliocene dispersal of these taxa into North America.