The turrilitid ammonoid Mariella from Hokkaido-Part1 : Studies of the Cretaceous ammonites from Hokkaido and Sakhalin-LXXXV

Abstract

Three species of the genus Mariella (Turrilitidae) from the Lower Cenomanian (Cretaceous) of Hokkaido are described. They include the two widespread species, M. (M.) dorsetensis (Spath, 1926) and M. (M.) oehlerti (Pervinquiere, 1910). The third species, M. (M.) pacifica sp. nov., is somewhat similar to but distinguished from M. (M.) oehlerti. It is also compared with some other species. The problem of dimorphism in the turrilitid ammonoids is discussed.