Latest evidence of Palaeoamasia (Mammalia, Embrithopoda) in Turkish Anatolia

ABSTRACT

Geological investigation of the Boyabat Basin in north-central Anatolia, Turkey, yielded palaeoamasid (Embrithopoda, Mammalia) gnathodental fossil specimens from two localities dated to the Eocene–Oligocene transition. These specimens include an upper incisor (BOY-1) and maxillary fragment preserving M2–M3 (BOY-2), and are geologically the youngest embrithopods known from Eurasia. The maxillary specimen is taxonomically more useful and, among embrithopods preserving the same molars, is most similar to the late Paleocene–middle Eocene Turkish palaeoamasid Palaeoamasia kansui. However, the new specimens are cautiously classified as Palaeoamasia, sp. nov., based on distinctions between BOY-2 and P. kansui in M3 morphology. Features distinguishing the M3 in BOY-2 are intermediate between those of P. kansui and the more derived Afro-Arabian arsinoitheriid embrithopods Arsinoitherium spp. and Namatherium blackcrowense, although the new Turkish specimens are stratigraphically too young to be ancestral to these middle Eocene–late Oligocene arsinoitheriids. Salient differences in dental and gnathic morphology between contemporaneous Eurasian and Afro-Arabian embrithopods indicate long, separate phylogenetic trajectories for these taxa, supporting the view that they are divisible at the family level into Palaeoamasidae and Arsinoitheriidae, respectively. Improved documentation of the lengthy paleogeographic separation of palaeoamasids and arsinoitheriids confirms that Afro-Arabia was sufficiently isolated from Eurasia during the Paleogene to limit embrithopods to rare sweepstakes dispersal between these landmasses.

ACKNOWLEDGMENTS

Field study of the Boyabat Basin was sponsored by the Hydro (presently Statoil) Research Center in Bergen, Norway. We thank A. Di Stefano and C. Agnini for their micropaleontological dating of our rock samples. The senior author (W.J.S.) is grateful to the following individuals and institutions for access to fossil specimens in their care: A. Jara, Authority for Research and Conservation of Cultural Heritage, the Ministry of Culture and Sports Affairs, Ethiopia; M. Yilma, National Museum of Ethiopia, Addis Ababa, Ethiopia; J. Hooker, Natural History Museum, London, United Kingdom; and M. Abdel Ghany, Cairo Geologial Museum, Egypt. Comparative study of embrithopods by the senior author was funded by a Scott Turner Award in Earth Science from the Department of Earth and Environmental Sciences, University of Michigan. We thank the late B. Miljour for expert preparation of the figures.

Handling editor: Marcelo Sanchez-Villagra.