Résumé
A new species of Sayimys (Ctenodactylidae, Mammalia), Sayimys giganteus sp. nov., is described from the Early Miocene localities of Kesekö y 1, Kesekö y 2, and Hisarcik (Turkey). Sayimys giganteus sp. nov. differs from other known species of Sayimys by its larger size and several plesiomorphies (e.g., metalophulid II on dp4, strong anterolophid and posterolophid on P4, and a long paraflexus and metaflexus on upper molars), but also in the presence of some derived characters. Two species of Sayimys are currently recognized in Turkey: Sayimys cf. Sayimys intermedius (at Paşalar, Middle Miocene) and Sayimys giganteus sp. nov. Based on a cladistic analysis involving all known species of Sayimys, Metasayimys, and Prosayimys, Sayimys giganteus sp. nov. emerges as the sister taxon of Sayimys obliquidens.