The hipparion from the late Pliocene of Ahl al Oughlam, Morocco, and a revision of the relationships of Pliocene and Pleistocene African hipparions

International audienceThis paper addresses three points: 1. the description of a new species (H. pomeli n.sp.) of Late Pliocene hipparion from Morocco; 2. preliminary notes on hipparion skulls from Langebaanweg E Quarry (H. hendeyi n.sp.) and Chad Kossoum Bougoudi; 3. a new interpretation of African hipparion relations. The Appendix presents practical techniques allowing the estimation of adult dimensions in juvenile skulls and correlations between two mandibular and skull dimensions. <br />H. pomeli was a medium-size species related to, but smaller than, H. hasumense from East Africa. The distance vomer-basion was small and there was no reduction of the third incisors. The lower cheek teeth were caballine, moderately hypsodont, with moderate ectostylids. The limb proportions were cursorial. H. pomeli differed from the true 'Eurygnathohippus' (H. afarense and H. cornelianum) by the basi-cranial proportions and the lack of reduction of the third incisors.<br />H. hendeyi had an extremely short vomer-basion distance, a short distance between the orbit and the POF, primitive teeth, and slender limb bones. It cannot be derived from H. africanum nor from H. turkanense. The greatest resemblances are with (the much smaller) H. moldavicum of Taraklia and H. giganteum of Grebeniki. The tentative reconstruction of H. feibeli's skull indicates a possible relation with H. hendeyi.<br />The very large skull from Kossoum Bougoudi, Chad, resembles but is much larger than, the Chinese H. dermatorhinum; its dimensions are compatible with the European H. crassum and the Mongolian H. tchicoicum.<br />It is proposed that more than two migrations gave rise to the various African species of hipparions