A new early cyclostome bryozoan from the Lower Ordovician (Volkhov Stage) of Russia

Goryunovia hemiseptata n. gen. n. sp. is an unusual Lower Ordovician cyclostome bryozoan, represented by a single colony from the Middle Volkhov Stage (Arenig) of the Leningrad Oblast. The encrusting uniserial colony consists of large, slender zooids, many with closely-spaced partial diaphragms (hemisepta), and has a distinctive trichotomous branching pattern. Skeletal organization is of the sagenellid grade: calcified interior walls appear to be present, and the exterior frontal walls lack pseudopores. As details of microstructure and early astogeny are unknown, it is difficult to interpret the phylogenetic relationships of Goryunovia until further material is forthcoming. However, there is some resemblance with the enigmatic hederellids, which appear in the Upper Silurian and possibly range into the Triassic.