Paleodietary reconstruction of Miocene faunas from Paşalar, Turkey using stable carbon and oxygen isotopes of fossil tooth enamel

Miocene-age (∼ 15 Ma) deposits at Paşalar in northwest Turkey contain abundant and well-preserved dental remains from a variety of herbivores. We used the carbon and oxygen isotopic compositions of inorganic carbonate in enamel from these teeth to reconstruct the paleodiet and sources of body water, respectively, of Miocene mammals. The δ¹³C (PDB) values of carbonate in the enamel fall between -13·5 and -9·0%, indicating a diet dominated by C₃ plants for all mammals. Some species are distinctly different isotopically from others, likely reflecting on variation in the δ¹³C values of the plants being consumed. Giraffokeryx and Caprotragoides display the most depleted δ¹³C values, probably indicating they were feeding upon C₃ plants experiencing low water stress and/or CO₂ recycling, such as in a forest. Hypsodontus and Conohyus, on the other hand, consistently display the most enriched δ¹³C values. They were therefore consuming isotopically enriched C₃ plants or a small quantity of C₄ grasses. In either case, a more open habitat is indicated. The other species we measured, including Griphopithecus, yielded intermediate values. The δ¹⁸O (PDB) values of the carbonate in fossil enamel also differ substantially between some taxa, and probably show that mammals such as Giraffokeryx, like East African giraffes today, were drawing their water from sources enriched in ¹⁸O, such as from the top of a forest canopy.