Report of an allodesmine humerus from Shimane, Japan: summary of Japanese allodesmines

ABSTRACT

A new specimen of a pinniped humerus was found from the middle Miocene Fujina Formation, Shimane, Japan. It was identified as Allodesminae gen. et sp. indet. based on morphological description and comparisons with allodesmine humeri. The results of the comparisons suggest that there is variation in morphological features within this group. This discovery that revealed allodesmines had already expanded along the north-to-south coastal regions from the early stage of the back-arc spreading of the Sea of Japan. According to the summary of Japanese allodesmines, these pinnipeds thrived in the Japanese coastal regions during the middle to late Miocene as well as in North America.

KEYWORDS:

• Allodesmines
• Miocene
• pinnipeds
• Sea of Japan
• Shimane

Acknowledgments

We would like to thank H. Sawamura (AMP); L. G. Barnes, J. Velez-Juarbe, and V. R. Rhue (LACM); H. Koike (Matsumoto Shiga Fossil Museum); Y. Tajima (NMNS); K. Ege and T. Irizuki (SMU); H. Endo (UMUT); and N. D. Pyenson and D. J. Bohaska (USNM) who facilitated access to museum collections of extant and extinct pinnipeds. We also thank N. Handa (then Shinshushinmachi Fossil Museum, now Museum of Osaka University) for access to the specimen and help to the project and K. Aotsuka, S. Takeda, and M. Yoshida (UMUT) for help to the investigation at UMUT. We are grateful to Y. Matsuura and N. Watanabe (Iwami Ginzan Geological Research Society) who helped with our field survey on the Oda coast. We would like to thank the editor of the journal, anonymous reviewer, and R. W. Boessenecker (College of Charleston) for providing useful comments.

Disclosure statement

No potential conflict of interest was reported by the authors.

Author contributions

W. T. examined the whole specimen, was responsible for taxonomic aspects, and wrote this paper. S. K. arranged the study, prepared SMU-KC-F0001, investigated the field survey, and wrote the geological part of this paper. K. O. arranged the study, and was responsible for taxonomic aspects. H. H. discovered SMU-KC-F0001, conducted the field survey, and reviewed the geological part of this paper. All authors reviewed this paper.

Supplementary material

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Additional information

Funding

This study was supported in part by the Sasakawa Scientific Research Grant from The Japan Science Society (number 2018-6032) and a donation from the W. T. Yoshimoto Foundation, Hawaii to W. T.