New early and middle Eocene artiodactyls from the Erlian Basin, Inner Mongolia, China

ABSTRACT

Eocene artiodactyls from Asia were considered less diverse and abundant than the contemporary perissodactyls, especially in the Eocene faunas from the Mongolia Plateau and Central Asia. By contrast, artiodactyls are highly diverse and endemic from the Eocene deposits of Europe and North America. Here we report two new genera and three new species of small- to medium-sized artiodactyls preserved by fragmentary materials from the Early and Middle Eocene of the Erlian Basin, Inner Mongolia, China. Paraphenacodus gabuniai sp. nov. represents the first record of artiodactyls from Arshantan Asian Land Mammal Age, and shows some more primitive characters than Paraphenacodus solivagus from the Middle Eocene of the Zaysan Depression of Kazakhstan. Although Paraphenacodus with generally bunodont teeth shows some similarities with both Early Eocene Tsaganohyus from Mongolia and early cebochoerid Gervachoerus from Europe, its affinities with other artiodactyls remain obscure. Two new genera and species, Irdinodon bicuspidata gen. et sp. nov. and Aliusuellus laolii gen. et sp. nov., from the Irdinmanhan ALMA represent new taxa of Lantianiinae and Tapirulidae, respectively. Irdinodon is characterized by twinned metaconules and entoconids on the upper and lower molars in lantianiines. Aliusuellus is characterized by a large size and a distinct ridge raised along the posterolingual side of the paracone to its apex on M2. These new artiodactyl materials from the Erlian Basin, as well as recently reported tapirulids and bunodont Erlianhyus, increase the diversity of the Eocene artiodactyls from the Mongolia Plateau, and provide new clues on the origin and dispersal of some early artiodactyls.

ACKNOWLEDGMENTS

We thank Q. Li, X. Jin, F.-Y. Mao, H.-B. Wang, W. Zhou, S.-J. Li, Qi Li, C.-K. Sun, Y.-X. Wang, Y.-F. Wang, R.-C. Xu, H. Xing, X.-Y. Zhang (all IVPP), K. C. Beard (University of Kansas, Lawrence, U.S.A.), and D. L. Gebo (Northern Illinois University, DeKalb, U.S.A.) for assistance in the field; X. Jin and W. Gao (both IVPP) for photography; Y.-M. Hou (IVPP) for μ-CT scanning; Y. Xu for the redrawing of Paraphenacodus solivagus in Figure 3j; Z.-Q. Zhang, B.-Y. Wang, X.-J. Ni, and S.-K. Hou (all IVPP) for helpful discussion. The suggestions and comments from two anonymous reviewers and editor A. Friscia greatly improved this manuscript. Funding was provided by grants from the Strategic Priority Research Program of Chinese Academy of Sciences (XDB26000000), the National Natural Science Foundation of China (42272011 and 41672014), Frick Funds from the Division of Paleontology, American Museum of Natural History, and a Discovery Grant from the Natural Sciences and Engineering Research Council of Canada (RGPIN/03433-2023).

DISCLOSURE STATEMENT

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

DATA AVAILABILITY STATEMENT

The CT scan data has been deposited in Admorph at this link: http://admorph.ivpp.ac.cn/sampleList.html?menuId=a1f2fa3c083e44b69890944db4d22f5c

AUTHOR CONTRIBUTIONS

BB and YQW designed the research and collected data. BB wrote the manuscript, analyzed data, and prepared the figures. JMT and JM improved and edited the manuscript. All authors reviewed the manuscript.

SUPPLEMENTARY FILE

Supplementary File 1.xlsx: Measurements for scatter plots.

Correction Statement

This article has been corrected with minor changes. These changes do not impact the academic content of the article.