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In the Djurab Desert (Chad), the fossiliferous sectors of Kossom Bougoudi, Kolle and Koro Toro have yielded a great amount of fossil hippo remains aged between ca. 5 and 3 Ma. Hippos from the first two areas represent a distinct lineage evolving in Chad during the early Pliocene. Indeed, a new species from Kolle is described (Hexaprotodon mingoz sp. nov.) and the Kossorn Bougoudi fossils may constitute its ancestral stem. At Koro Toro, a different but very rare form occurs, and its affinities remain unclear. These hippopotamids testify to a more complex family history than previously recognized, and reinforce the idea of using this group for biochronology. The hippos underscore relative endemism of the Chadian fossil faunas and would indicate a greater and earlier aridity of this region in contrast to East Africa. (C) 2003 Elsevier Science Ltd. All rights reserved.