Revision of the Family Chiastoclonellidae Rauff, 1895 (Porifera, Orchocladina)

Within the sponge family Chiastoclonellidae (Rauff, 1895) two new sub-families are erected: (1) the early Palaeozoic Eochiastoclonellinae; (2) the Late Palaeozoic Neochiastoclonellinae. This study focuces on the Eochiastoclonellinae, which mainly originate from Baltica. All in all, six genera and eleven species are distinguished within this taxon. Information derived from new material leads the authors to split Chiastoclonella sp. Van Kempen, 1990 into the new species C. globula n. sp. and C. incrustans n. sp. The unique specimen of Domospongia silurica Schlüter, 1887, which was re-assigned by Rauff in 1895 to Aulocopium aurantium Oswald, 1847, is restored to its original name. Based on the evidence of new specimens, the diagnosis of Syltispongia ingemariae Van Kempen, 1990 is revised and Diotricheum vonhachti Van Kempen, 1990 is moved from the Anthaspidellidae to the Eochiastoclonellinae. The eochiastoclonellid Baltic sponges comprise calcareous sponge bodies from bedrock strata in Estonia and West Russia and silicified erratic sponges from glacial/fluvial deposits in the Netherlands, Germany, and Gotland, Sweden. The erratic chiastoclonellids form part of a large body of erratic sponges, dominated by Astylospongiidae and Anthaspidellidae. On both lithological and palaeontological grounds, this group can be divided into ‘blue’ sponges, associated with Lavenderblue Chert of Sandbian and Katian age, and ‘brown’ sponges, associated with Brown Pirgu Chert of Katian age. Most erratic chiastoclonellids are ‘brown’ sponges, but there is a significant minority of ‘blue’ specimens. The ‘brown’ and ‘blue’ sponge assemblages have a different provenance, but probably all originate from within the North Estonian confacies belt. Their body shape suggests that the Baltic eochiastoclonellids lived on a seabed of loose carbonate sediment in shallow, moderately warm water. Two new genera and five new species are described: Wilsumispongia, represented by W. cylindrica, W. cratera and W. conica, and Chiastodiscus, represented by C. verrucosus and C. regularis.