Basal hippopotamines from the upper Miocene of Chorora, Ethiopia

ABSTRACT

The Hippopotamidae have been a major component of the African wetland fauna for the last 7 million years, following the ‘Hippopotamine Event,’ i.e., the sudden emergence in the fossil record of the subfamily Hippopotaminae, including both extant species. The general dearth of African fossiliferous deposits dated between 9.5 Ma and 7.5 Ma concealed until now the evolution that led to the Hippopotamine Event and the subsequent success of these large semiaquatic herbivores. Part of this evolution is unveiled by the hippopotamid dental remains found at Chorora, a late Miocene site of the southern Afar Depression in Ethiopia spanning most of the fossil-depleted time interval. Although fragmentary, these remains represent a new, mid-sized hippopotamid species dated to ca. 8 Ma, as well as a somewhat younger, larger form. A cladistic analysis of a large array of cetartiodactyls indicates that the Chorora taxa were basal to the latest Miocene hippopotamines. The new species displays a mosaic of dental characters that support the attribution of the new species to a new genus within Hippopotaminae. The new fossils also clarify the course of early hippopotamine dental evolution. The Chorora hippopotamids suggest that transition to a marked abundance of hippopotamines with their unique dental pattern in African ecosystems occurred within a relatively short time interval, most probably between 8 Ma and 7.5 Ma.

http://zoobank.org/urn:lsid:zoobank.org:pub:47B9381F-E3B5-40C9-B9AB-51CC3D0D3A8A

SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at www.tandfonline.com/UJVP

Citation for this article: Boisserie, J.-R., G. Suwa, B. Asfaw, F. Lihoreau, R. L. Bernor, S. Katoh, and Y. Beyene. 2017. Basal hippopotamines from the upper Miocene of Chorora, Ethiopia. Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2017.1297718.

ACKNOWLEDGMENTS

We thank the Authority for Research and Conservation of Cultural Heritage (ARCCH), Ministry of Culture and Tourism of Ethiopia, for permissions and facilitation of the field work. We thank the Western Hararge Chiro Zone Culture and Tourism Office and the Mieso Woreda for field work support. We thank all participants in the field work, especially the Gololcha people, who were essential to the success of the project. We also thank two anonymous reviewers for their comments that improved the manuscript. The Chorora paleoanthropological project was supported primarily by the Japan Society for the Promotion of Science (Kakenhi grant numbers 21255005 and 24000015). J.-R.B. would like to thank the following institutions for providing access to study the comparative materials: ARCCH; Staatliches Museum für Naturkunde Karlsruhe; Abu Dhabi Tourism & Culture Authority; Centre National de la Recherche pour le Développement, N'Djaména; National Museums of Kenya, Nairobi; and Office National des Mines, Tunis. Access to the Chorora material stored at the ARCCH was greatly facilitated by Tomas Getachew and Getahun Tekle. Kebedde Geleta kindly helped with Oromo spelling. This study was performed with the support of SPLASH, research program ANR-15-CE32-0010-01 of the Agence Nationale pour la Recherche.