Abstract: The Salyan Formation (Upper Burdigalian-Lower Langhian) of K. Maraş, Turkey contains thick-beddeddeposits of oysters. Bioerosion structures found on the Early-Middle Miocene oyster specimensCrassostrea gyrphoides (Schlotheim, 1813) from the Northwestern K. Maraş Basin area are muchaffected by the boring of micro-organisms. The borings, represented by three ichnogenera, are assignedto Renichnus isp., Caulostrepsis isp., and Entobia isp. The activity of Clionid sponges, Polychaeteworms and vermetid gastropods have also been observed.