Inoceramid bivalves at the Turonian/Coniacian boundary: biostratigraphy, events and diversity trend

The Turonian/Coniacian boundary marks one of the main turnover levels in the Late Cretaceous history of the inoceramid bivalves. The change from the Mytiloides-dominated Late Turonian fauna to the Cremnoceramus-dominated Early Coniacian fauna was a dramatic experience for the group, with a series of successive assemblages interrupted by their almost total elimination, and with intervening short-term expansions of the bivalve Didymotis. The taxonomic diversity dropped to a few species per interval calculated and marks the lowest level in their Late Cretaceous history, comparable to the trough around the Cenomanian/Turonian boundary. The whole change must have taken no longer than a quarter of a milion years and its duration could have been as short as some tens of thousand years