Trochoceramid bivalves (Inoceramidae) from the Lower Maastrichtian of Daghestan (Aimaki section, NE Caucasus) and south-central Poland

Abstract

The representatives of the inoceramid genus Trochoceramus HEINZ, from the Lower Maastrichtian of Daghestan (NE Caucasus) and south-central Poland are described. Four species are recognized in the material from Daghestan and also the same number, though represented by other species, in the material from Poland. This difference is probably the result of different facies conditions in the Early Maastrichtian sea in both areas. The first appearance datum of the genus Trochoceramus seems to approximate the Campanian - Maastrichtian boundary, thus providing a valuable biostratigraphic tool for chronostratigraphic correlation. The previously cited long range of the genus within the Upper Campanian was based on poorly known occurrences, and it seems that the genus is limited to the Lower (and ?lowermost Upper) Maastrichtian.