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

ABSTRACT

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.

KEYWORDS:

• Microtodon
• Promimomys
• Baranomys
• late Miocene
• early Pliocene
• arvicoline-like rodents

Acknowledgments

We are indebted to K. Hordijk of the Institute of Earth Sciences Utrecht, L. Maul of the Senckenberg Research Institute, A. Nadachowski, Polish Academy of Sciences, A. S. Tesakov of the Russian Academy of Sciences, for providing observations and information on arvicoline-like cricetids. We are grateful to P. Holroyd for her help in curating the specimens and allowing us access to the collections at the UCMP. Maxim Sinitsa and an anonymous reviewer provided constructive comments on the original draft of this paper.

Disclosure statement

No potential conflict of interest was reported by the author(s).