Bryozoans from the Pliocene Coralline Crag of Suffolk: a brief review

The Coralline Crag Formation is a bryozoan-rich, cool-water limestone of Early Pliocene age. The small outcrop area of the formation in eastern Suffolk belies its great historical and scientific importance. Approximately 140 species of cyclostome and cheilostome bryozoans occur in the Coralline Crag, many with interesting ecologies, palaeoclimatic significance or unusual biogeographical distributions. However, the Coralline Crag bryozoan fauna has remained unrevised since the publication in 1859 of George Busk’s seminal monograph, although some taxonomic groups have been treated individually. Bryozoan evidence points to a warmer sea during Coralline Crag deposition than that of the present day. Preliminary data indicate that slightly more than half of the bryozoan species in the Coralline Crag are extinct, with a higher proportion of extinct species among the cyclostomes than the cheilostomes. Several of the more distinctive bryozoans in the Coralline Crag, including the massive cyclostomes Blumenbachium and Meandropora, as well as Heteropora, ?Retihornera and Melicerita, appear most closely related to bryozoans no longer inhabiting British waters but still living in the southern hemisphere. The Coralline Crag represents one of the last examples of a formerly more widespread bryozoan fauna dispersed via the Tethys before climatic deterioration brought about widespread extinctions.