We describe two new species of esthonioporate
bryozoans, Revalotrypa inopinata sp. nov. and R. yugaensis
sp. nov., from the Lower Ordovician, south-east of Lake
Ladoga, north-western Russia. The colonies of the two
species are very small and were extracted from limestone
nodules found in the lower part of glauconitic sandstone in
the Joa Member (lowermost Floian). Revalotrypa inopinata
sp. nov. and R. yugaensis sp. nov. are the oldest known
bryozoans from Baltoscandia. Study of the two species
includes scanning electron microscopy (SEM) imaging and
X-ray microtomography (micro-CT). The palaeogeo-
graphic distribution of the oldest known bryozoans from
the Lower Ordovician and the advantages and disadvan-
tages of micro-CT for the study of Palaeozoic bryozoans
are discussed. The authorship of Revalotrypidae, which has
been inconsistently allocated in the literature, is discussed.