Abstract: A diverse and abundant Early Eocene (middle-late Cuisian) molluscs assemblage from the YoncalıFormation of the Çankırı Basin in central Anatolia is documented for the first time in this study. Sixspecies of bivalves, four species of gastropods, and one species of scaphopod are described from theformation. The central part of the Yoncalı Formation consists mostly of sandstones, pelagic mudstoneand limestones with harpactocarcinids and the molluscs found were derived from this part. Associatedfauna found here included benthic foraminiferans, serpulids, undetermined echinoids and shark teeth,and dating was mainly based on the benthic foraminiferans. The distribution of bivalve, gastropod andscaphopod species suggest that this area has affinities with the East European Province of Turkey. Thecosmopolitian distribution of the recorded species is useful for paleobiogeographic reconstruction. Thisreveals that there was a direct connection throughout the Tethyan realm and a connection between theTethyan central Anatolia and Indo-Pasific realms, at least until the end of the Paleocene to Early Eocene(Early Tertiary), and this allowed the migration of benthic organisms.