Early Maastrichtian cheilostome bryozoans from the middle Volga River region

Abstract

Eight species in six genera of cheilostome bryozoans are described from an early Maastrichtian outcrop located in the Saratov Region, middle Volga River region, southern Russia. The studied bryozoan assemblage includes a new species, Cheethamia volgaensis sp. nov., as well as Dionella sp., Cheethamia aktolagayensis Koromyslova et al., Rhagasostoma cf. saltans (Brydone), and Luganella goldfussi (von Hagenow). A few poorly preserved specimens are tentatively assigned to the genera Hoplitaechmella and Acoscinopleura. Some of the recorded species encrusted a Cataceramus shell and internal moulds of Baculites ammonoid shell fragments; whereas others produced erect, flattened, bifoliate colonies. A single species, L. goldfussi, had free-living, discoidal colonies. The palaeobiogeography of early Maastrichtian bryozoans is discussed. The recorded bryozoans belong to genera ubiquitous in the early Maastrichtian of Europe and, to a lesser degree, other regions.