Bathonian (middle jurassic) cyclostome bryozoans from the Polish Jura

Abstract

Cyclostome bryozoan assemblages encrusting bivalve shells and oncoliths, as well as coming from the host sediment, are described from the Bathonian (Middle Jurassic) ore-bearing clays of the Polish Jura. In total, 16 species belonging to the genera Stomatopora, Proboscinopora?, Microeciella, Reptomultisparsa, Hyporosopora, Mecynoecia, Ceriocava and unidentified 'entalophorids' are described. Twelve taxa could not be determined with certainty to species level. Two species are described as new: Reptomultisparsa kawodrzanensis sp. nov. and Mecynoecia kaimi sp. nov. The diagnosis of Hyporosopora bugajensis Zatoń & Taylor, 2009a is emended. Combining the diversity data both from this and a previously published paper, a total of 29 species of cyclostome bryozoans are now known from the Bathonian of the Polish Basin, a stratigraphical stage during which the cyclostomes attained their peak-diversity for the Jurassic. This species richness is comparatively high, approaching the maximum recorded for a Jurassic assemblage, which is 33 species in the Bathonian of Normandy, France where the bryozoans are associated with sponge bioherms and hardgrounds as well as oncoliths and shells of bivalves and brachiopods.