Ordovician chitinozoan zones from Baltoscandia

On the basis of reports published over the last 60 years, and unpublished data, a chitinozoan zonation is proposed for the Ordovician sequence of Scandinavia, the East Baltic, northeast Poland and Podolia commonly referred to as Baltoscandia. From the first chitinozoans in the latest Tremadoc to the latest Ashgill (a period comprising ca. 52 My) 15 zones and 8 subzones arc defined, each corresponding to some 1-5 My. These are compared with the graptolite and conodom zonations. The greatest precision is achieved in the succession beginning with the conodont Zone of Amorphognathus tvaerensis, and ending with the lop of the Ordovician, where chitinozoan stratigraphic evolution surpassed that of olher taunal elements. Important associated chitinozoan species in each zone and subzone are discussed.