A new cricetid rodent from the early Oligocene of Yunnan, China, and its evolutionary implications for early Eurasian cricetids

ABSTRACT

Here we report a new early Oligocene cricetid, Paracricetops virgatoincisus, gen. et sp. nov., discovered from the Caijiachong locality in Yunnan Province, China. This new cricetid shows a peculiar combination of characters, such as massive and transversely positioned cusps, crenulated cheek tooth enamel, and a deep fossette enclosed between protocone and paracone. These characters are also present in Cricetops, a cricetid rodent of which the phylogenetic relationship with other cricetids remains debatable. Our phylogenetic analysis based on a data matrix including 37 taxa and 67 morphological characters reveals that Paracricetops and Cricetops are sister groups. Paracricetops, Cricetops, Deperetomys, Meteamys, Selenomys, Melissiodon, Mirrabella, Enginia, Muhsinia, and Aralocricetodon constitute a monophyletic group. This result suggests that these genera should all be grouped in the subfamily Cricetopinae. Our phylogenetic analysis also casts new lights on the origin and early radiation of the family Cricetidae. The subfamily Pappocricetodontinae is a polyphyletic group. Pappocricetodon and Raricricetodon, two basal cricetid genera, are also polyphyletic. A thorough systematic revision of these basal cricetids is needed. Chronological distribution of Eucricetodontinae, Paracricetodontinae, Pseudocricetodontinae, and Cricetopinae indicates that the establishment of these cricetid clades should be in the late Eocene at least. We therefore deduced that the first diversification and dispersal of the family Cricetidae across Eurasia must have occurred well before the Eocene-Oligocene transition.

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ACKNOWLEDGMENTS

We are grateful to L. J. Flynn, M. Hugueney, J. Meng, B. Wang, and Q. Li for helpful discussions about the evolution of cricetids. W. Zhang took the SEM pictures of the material. We also extend our gratitude to the reviewers, M. Dawson, D. Kalthoff, and H. Gomes Rodrigues, for their instructive comments and suggestions. This project has been financially supported by the National Basic Research Program of China (2012CB821904), Chines Academy of Sciences (CAS) Young Scholar Project, CAS 100-Talent Program, CAS Fossil Excavation and Preparation Fund, and the National Natural Science Foundation of China (NSFC 40672009, 40872032). O.M.'s research is supported by the NSFC (41050110135) and the Research Fellowships for International Young Researchers of the Chinese Academy of Sciences (No. 2009Y2BZ3).

Handling editor: Thomas Martin