The Chalicotheriidae (Mammalia, Perissodactyla) from the upper Miocene Nakali Formation, Kenya

ABSTRACT

Two upper molars of the Chalicotheriidae (Mammalia, Perissodactyla) from the upper Miocene (ca. 10 Ma) Nakali Formation of Nakali, central Kenya, are described. One is identified as M2. The other is very fragmentary and is tentatively referred to the same species as the M2. The M2 specimen is assigned to the subfamily Schizotheriinae in having a crown longer than wide and higher than that of the Chalicotheriinae. It is morphologically similar to upper molars of late Miocene and Plio-Pleistocene species of the Schizotheriinae such as Ancylotherium pentelicum and Ancylotherium hennigi. Metrically, the M2 is within the range of A. pentelicum, resulting an identification as Ancylotherium cf. pentelicum. This result suggests that the fossil record of this genus in Africa dates back to ca. 10 Ma. Previous and present studies suggest that Miocene African Ancylotherium would have been in forest-dominated environments. African and Eurasian fossil records of Ancylotherium suggest that the dispersal of this genus from Eurasia into Africa would have occurred before ca. 10 Ma, although more African fossil records are needed to confirm this.

KEYWORDS:

• Africa
• Ancylotherium
• Chalicotheriidae
• late Miocene
• Schizotheriinae

Acknowledgments

We wish to thank the National Commission for Science, Technology and Innovation (NACOSTI), the Government of Kenya and the National Museums of Kenya for research permission. We thank the staff of the National Museums of Kenya for assistance in the museum. The first author is grateful to Christine Argot (Muséum National d’Histoire Naturelle, Paris, France) and Gertrud Rößner (Bayerische Staatssammlung für Paläontologie und Geologie, Munich, Germany) for providing access to specimens for the comparative works. We wish to thank Editor in chief Gareth Dyke and two anonymous reviewers, whose comments improved the original manuscript. 

Disre statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the JSPS (Japan Society for the Promotion of Science) KAKENHI [22255006, 25257408, 16H02757 to M. Nakatsukasa, and 18K13648 to N. Handa].