The core of the Gaindinskaya-3 reference borehole disclosing a complete section of Ordovician deposits in the basin of the middle reaches of the Podkamennaya Tunguska River has yielded a diverse ostracod assemblage, which supplements the paleontological characteristics of the Upper Ordovician of the Siberian Platform. Three new genera and 14 new species are described; the previously known taxa are provided with photographs. The characteristics of stratigraphic distribution of ostracod assemblages in the section of the core are considered and boundaries between some regional stages and ostracod biozones are revised.
