Chitinozoan diversity in the East Baltic Silurian

Data on the diversity of the East Baltic Silurian chitinozoans have been compared to global chitinozoan biozones that are approximately correlated with the graptolite scale. The total diversity and balanced total diversity curves have three main positive peaks in the Wenlock and Ludlow and diversity lowstands in most of the Llandovery and Pridoli. The turnover ratio and species origination curves are lowest and species extinction is highest in the lower Wenlock, correlating partly with the Ireviken Event. Chitinozoan diversity is related to the transgression-regression phases of the Silurian Baltic basin, water chemistry and temperature, and evolutionary processes of the faunal group. At the level of the Silurian standard stages the trends in the East Baltic and Swedish chitinozoan diversity curves are in general outline similar to the global diversity curve.