Down to the roots of lemmings: a new species of basal lemming from the upper Pliocene of West Siberia

ABSTRACT

A previously unknown evolutionary stage of true lemmings, Lemmini, is recorded in the lower upper Pliocene (early Villanyian, MN16a) of West Siberia. Tobienia fejfari, sp. nov. represents a more advanced evolutionary stage than the previously known European Tobienia kretzoii (late Ruscinian, MN15b), combining rhizodont molar teeth with extreme hypsodonty, crown cement, and occlusal morphology resembling the earliest lemming with rootless molars, Plioctomys, of later Late Pliocene age (MN16b). The new discovery contributes to our knowledge of early stages in the formation of the high latitude mammalian fauna of Eurasia.

ACKNOWLEDGMENTS

We thank A.L. Dorogov, A.D. Sorokin, and N. Antonyuk (all from Omsk), and S.A. Sokolov and A.A. Yakimova (Moscow) for their help during fieldwork. E.V. Syromyatnikova (Paleontological Institute RAS, Moscow) is thanked for preliminary determination of herpetofauna. Two reviewers, R.A. Martin and Y. Kimura, are acknowledged for valuable corrections and suggestions. E.A. Markova (Yekaterinburg) suggested important improvements of the text. Engineering staff of Paleontological Institute RAS (Moscow) is thanked for the help with SEM microscopy. The study corresponds to the state topics of scientific research of the Geological Institute of the Russian Academy of Sciences.