The new gonyaulacoid dinoflagellate Pentadinium galileoi Sancay et al., sp. nov. from the Oligocene-Lower Miocene sediments of Eastern Anatolia has been identified. It is spherical, chordate with prominant discoidal cingulum and distally furcate apical, sulcal, and antapical processes. It has a type P(3???) archeopyle, and periarcheopyle is larger than endoarcheopyle. Tabulation is distinct and it has a formula of 1pr, 3-4',6???,6c,6???', 1p,1??????, Wall structure is granular in intraplate areas, and it has gonal spines at apex, posterior intercalary, and antapex. Processes at gonal positions may be on a variably developed antapical 'skirt' formed by extended septa (2-3 ??m), minute bifurcate spines intergonally and along cingulum at plate intersections. Periphragm and endophragm appressed except at cingular area and at septa. The size of the cysts ranges between 73-89??m with an avarage of 84??m.