LAUSR

Chitinozoans are a key group in Ordovician and Silurian biostratigraphy, and the Baltic region hosts some of the largest collections of these microfossils in the world. Here, we present an online database – ‘CHITDB’ – for documenting and analysing the distribution of chitinozoans in the Baltic region. The system is integrated with the Estonian geocollections database and includes a public query portal ( ), which allows browsing and searching for chitinozoan taxa, samples, sections, references and SEM images, downloading raw data by sections, and generating range charts, summary reports and CONOP9 input files. The chitinozoan database holds currently over 35000 occurrence records of 300 chitinozoan taxa from 6400 micro-palaeontological samples and 100 sections. Quantitative stratigraphical analysis of this data set enabled compilation of the highest resolution chitinozoan diversity curves through the Ordovician and Silurian to date, and assessment of the rates of evolutionary changes. The new model incorporates K-bentonite and carbon isotope data that help to constrain time relationships between bioevents and environmental changes. The highest chitinozoan diversity in the Baltic region is encountered in late Darriwilian to mid-Katian and in the Telychian, when the standing diversity reached 30–35 species. Overall, the latest Ordovician and Silurian faunas show more dynamic diversity patterns, with higher extinction and origination rates, than was typical for most of the Ordovician Period.