Miocene to Pleistocene Hipparions of Kenya, Tanzania and Ethiopia

CONTENTS Introduction and acknowledgements............ 3 Some notes on working methods............. 5 Species of Hipparion in Africa............. 6 Hipparion primigenium (Von Meyer)............ 12 Hipparion turkanense Hooijer & Maglio........... 19 Hipparion? aff. sitifense Pomel............. 22 The Olduvai Gorge Hipparion: Hipparion cf. ethiopicum (Joleaud) .... 26 The Omo Group Hipparion: Hipparion spec. and Hipparion ethiopicum (Joleaud) 52 References................... 73 Explanation of the plates............... 76 INTRODUCTION AND ACKNOWLEDGEMENTS Hipparion De Christol, 1832, comprises extinct tridactyl equids typified by their isolated protocones, which evolved in North America from Merychippus stock, and invaded the Old World 12.5 million years ago. Gone are the days when Hipparion was considered ancestral to Equus, but to this day sweeping conclusions are being drawn about some reduction in the length of the side metapodials relative to the median metapodial from the oldest to the youngest forms, whereas in reality all there was is allometric growth (cf. Forsten, 1973a). In her plea for the new systematics, with polytypic rather than local and chronologically limited species, Forsten (1973b) observes that since 1829, when the first finds were described by Von Meyer, until about 1930 new species of Hipparion have been described at a mean rate of one every three years. Since 1930, the mean rate of increase in the number of species described as new in Hipparion has been two every three