A fossil elasmobranch assemblage was found from the Middle Miocene Lower Formation, Bihoku Group and Yoshino Formation, Katsuta Group, Okayama Prefecture. Fossiliferous sediments are black mudstone and muddy sandstone deposited in an intertidal environment. Hydrogen peroxide was employed to disrupt the muddy matrix of the sediments. Wet screening and microscopic sorting have produced 73 isolated elasmobranch teeth and 18 placoid scales. These specimens consist of Dasyatis (stingray), Carcharhinus (ex., blacktip reef shark), Squatina (angel shark), and some unknown genera. Dasyatis is the most dominant genus across both formations, accounting for 81% of all tooth specimens. This fossil elasmobranch assemblage suggests that a stingray-rich elasmobranch fauna existed in the Middle Miocene Setouchi Geologic Province.
