Two New Ammonoid Genera of the Subfamily Gabbioceratinae from the Upper Albian (Lower Cretaceous) of Hokkaido, Japan

Two ammonoids of the subfamily Gabbioceratinae, Obataceras manjiense gen. et sp. nov. and Tanabeceras pombetsense gen. et sp. nov., are described from the Upper Albian of Hokkaido, Japan. The Gabbioceratinae evolved and radiated mainly in the Mediterranean area during Late Aptian to Middle Albian times, but thereafter disappeared from the region. The occurrences of Gabbioceratinae in Hokkaido suggest that their geographical distribution was extended to the Northwest Pacific before the Late Albian, where they then flourished from Late Albian to Cenomanian time.