Botryllopora (Cystoporata, Bryozoa) from the Middle Devonian of Canada and Germany

Botryllopora (Cystoporata, Bryozoa) from the Middle Devonian of Canada and Germany - The Middle Devonian cystoporate Botryllopora Nicholson, 1874 is known from the type species Botryllopora socialis Nicholson, 1874 which was originally described from the Hamilton Formation of Arkona, Ontario, Canada. The discovery of new material of B. socialis in Germany has prompted a revision of this peculiar cystoporate using material from Ontario as well as the new German locality. The latter comprises 32 colonies discovered in the Ahbach Formation, lowermost lower Givetian (hemiansatus Conodont Biozone) of the abandoned ‘Müllertchen Quarry’ near the village of Ahütte (Rhineland Palatinate, western Germany) within the Hillesheim Syncline (Eifel, Rhenish Massif). Colonies of
Botryllopora are encrusting and compound, comprising multiple subcolonies each with a central macula consisting of vesicles and surrounded by about 10 radial fascicles of biserial autozooidal apertures. Each macula can be inferred to have functioned as the site of an exhalent chimney for centripetally directed water filtered by the autozooids. The Ordovician-Silurian genus Inconobotopora is similar but has simple conical colonies that may have lived partly embedded in soft sediment. Together these two genera constitute Botrylloporidae, a Palaeozoic cystoporate family showing striking convergences with post-Palaeozoic lichenoporid cyclostomes reflecting commonality in the pattern of their multizooidal feeding currents. Many subcolonies of Botryllopora possess enlarged vesicles at their edges with apertures directed towards the centres of the subcolonies. Previously undescribed among cystoporate bryozoans, these structures are very tentatively inferred to be brood chambers, the released larvae being channelled towards the closest macula for expulsion.