Baltic Ordovician compound sponges as erratics on Gotland (Sweden), in northern Germany and the eastern Netherlands

Abstract Compound orchocladine sponges are unusual in the Early Palaeozoic. In Europe, silicified material of Late Ordovician age has hitherto been referred to as Aulocopium aurantium Oswald, 1847 and the invalid Aulocopium compositium Conwentz, 1905. An examination of new material has resulted in the recognition of a new genus, Hydraspongia , with two new species, H. polycephala and H. erecta , and a third new species, Perissocoelia megahabra , to which most specimens can now be assigned. These taxa form part of rich erratic sponge assemblages, which originate from unknown source areas in the... Mehr ...