Cormohipparion cappadocium, a new species from the Late Miocene of Yeniyaylacık, Türkiye, and the emergence of western Eurasian hipparion bioprovinciality

We studied the Vallesian records from Türkiye and Iran, and uncovered a diverse record of Cormohipparion species from Yeniyaylacık and Sinap, Türkiye, and their apparent descendant, Hipparion gettyi from Maragheh, Iran. This prompted us to examine the early evolutionary diversification, biogeography and paleoclimatology of western Eurasian hipparions. Our study also included the early hipparion records from Austria, Germany and the Iberian Peninsula. Whereas the Vienna Basin, Austria, has the oldest recorded occurrence of Hippotherium sp. at 11.4–11.0 Ma, our investigation revealed that the most primitive Old World hipparions belonged to the North American genus Cormohipparion. We integrated the data on crania, dentitions, 3rd metacarpals and 3rd metatarsals to further evaluate the systematics of Vallesian hipparions (11.2–9.6 Ma). Sinap, Türkiye, has the most primitive Cormohipparion in Eurasia, Co. sinapensis, but based on postcranial anatomy, we found that also Co. kecigibi is a second Cormohipparion species of Sinap's early Vallesian. The locality of Yeniyaylacık, Türkiye, dated ca. 9.1 Ma, has the latest occurrence of Eurasian Cormohipparion, Co. cappadocium. Our analyses also revealed that the genus Hipparion sensu stricto was probably directly derived from Subparatethyan (including Türkiye) Cormohipparion, with the most primitive taxa being Hipparion gettyi and Hipparion prostylum. Hipparion gettyi first occurred at Maragheh, Iran, ca. 9.0 Ma at the end of MN 10. Hipparion sensu stricto includes H. gettyi, H. prostylum, H. dietrichi and H. hippidiodus and had a range that extended from France through Greece and Türkiye to China.