Famennian (Late Devonian) ostracods of the Thuringian Mega-Assemblage were recovered for the first time from three incomplete sections of the Ayineburnu Member of the Büyükada Formation in the Denizliköy area (Gebze, NW Turkey), which were sampled for conodonts. Conodont faunas define an interval extending from the Upper rhomboidea? or Lower marginifera Zone into the Middle expansa Zone of the standard Upper Devonian conodont zonation. The ostracod faunas found here consist of species mainly with thin-walls, long spines and often smooth surfaces such as Rectonaria, Tricornina, Orthonaria, Triplacera, Beckerhealdia, Timorhealdia, Bohemina, Paraberounella and Acratia. These taxa indicate faunal relationship with Thuringia and the Rhenish Massif in Germany, the Cantabrian Mountains and Pyrenees in Spain, Holy Cross Mountains in Poland, North Africa and China.