New dipodid rodents from the Late Eocene of Erden Obo (Nei Mongol, China)

Abstract

New dipodid occurrences (Heosminthus nomogenesis sp. nov., Sinosminthus sp., Allosminthus cf. A. majusculus, Allosminthus ernos and Allosminthus cf. A. diconjugatus) are reported from the ‘Upper Red’ beds of the Erden Obo section in Nei Mongol, China. Heosminthus nomogenesis is similar to Heosminthus primiveris from the Caijiachong Formation, and it is more primitive than Heosminthus chimidae of the Mongolian biozone A. Allosminthus cf. A. majusculus has a more variable mesolophid and metalophid in m1-2. Based on the dipodid assemblage, the age of the ‘Upper Red’ of the Erden Obo section is late Eocene and correlative to the Ergilian. Based on the comparison of their morphological characters, we recognize some differences between the stem dipodoids and muroids.

Keywords:

• Mammalia
• dipodid
• Eocene
• Nei Mongol
• Erden Obo

Acknowledgements

We thank Bin Bai, Xun Jin, Ping Li, Jin Meng, K. C. Beard, D. L. Gebo, Xijun Ni, Wei Chen, Wei Zhou, Shejie Li, Qiang Cao, Wei Gao, Chenkai Sun, Fangyuan Mao, Haibin Wang, Yongxin Wang, and Qi Li for assistance in fieldwork, and Yongfu Wang for specimen preparation. Hongwei Si and Wengding Zhang for assistance in SEM. Yong Xu for assistance in drawing. Judith A. Schiebout helped to improve the manuscript. We thank the two anonymous reviewers for their critical and helpful reviews and Dr. Dyke Gareth for instructive editorial comments.