New findings of the genus Revalotrypa, the oldest bryozoan genus of Baltoscandia, in north-western Russia

Abstract

New findings of esthonioporate bryozoans of the species Revalotrypa cf. inopinata, representing one of the oldest bryozoans of Baltoscandia, are described from an outcrop located in Leningrad Oblast' (north-western Russia). The colonies of this species are very small and were extracted from limestone-cemented nodules found in glauconitic sandstones of the lower part of the Joa Member (Paroistodus proteus conodont zone, lowermost Floian, Lower Ordovician). Combined X-ray microtomography and the examination of traditional thin sections under a stereomicroscope and a light microscope were used to study the morphology of this species.