CAMBRIAN BRACHIOPODS OF THE SUBPHYLUM RHYNCHONELLIFORMEA FROM THE SIBERIAN PLATFORM ( systematic composition, facies association, and paleogeographic distribution )

This paper analyzes published data and brachiopod collections available to the authors to determine the systematic composition of brachiopods of the subphylum Rhynchonelliformea from the Cambrian formations of the Siberian Platform. To date, 50 species and 1 taxon identified to the genus level (Finkelnburgia sp.) have been described. These belong to 15 genera, 10 families (family assignment for two genera remains unclear), and 5 classes. Cambrian brachiopods of the subphylum Rhynchonelliformea from the Siberian Platform can be divided into six associations, each characterized by a specific taxonomic composition, paleogeographic distribution, and stratigraphic range. The most representative brachiopods belong to the class Obolellata. Specimens of this class have been found in North America and Greenland, allowing for relatively confident correlation of Lower Cambrian deposits between North America and the Siberian Platform. The class Strophomenata is also widely distributed. However, of the ten Siberian species of the genus Billingsella Hall & Clarke, eight are endemic. Thus, the occurrences of these brachiopods can be effectively used for genus-level correlation of transitional strata between the Middle and Upper Cambrian. Representatives of other classes (Chileata, Kutorginata, and Rhynchonellata) have lower potential for interregional correlation, although some of them have been found in other regions of the world and can serve as additional tools for correlating distant sections.