Database and species diversity of Japanese Cretaceous ammonoids

A total of 790 ammonoid species are recorded from the Cretaceous of Japan using a database of Japanese Cretaceous ammonoids. The species diversity changes of these ammonoids over the course of 31 Japanese Cretaceous substages are described. Seven peaks of high diversity and six events of minimal diversity are elucidated for the Cretaceous of Japan. The times of ammonoid species diversity minima are approximately correlated with oceanic anoxic events, OAE1 to 3, which seems to indicate that species diversity for the Japanese Cretaceous ammonoids was influenced by oceanic anoxic events/subevents.