Bryozoans of the Latorp and Volkhov horizons (Lower-Middle Ordovician) of the Leningrad Region

This monograph deals with the morphology of bryozoans of the orders Cystoporida and Trepostomida from the Latorp and Volkhov horizons (Lower–Middle Ordovician, Floian–Darriwilian stages) of the Leningrad Region. Diagnoses of some families belonging to these orders are revised. Based on morphological features of the bryozoans studied and on the succession of their taxa, four assemblages and three stages in their development are established. In addition, the stratigraphic and paleogeographic distributional patterns of bryozoans in the Lower and Middle Ordovician of the world are analyzed.