Encrustation and bioerosion on late Sheinwoodian (Wenlock, Silurian) stromatoporoids from Saaremaa, Estonia

A shallow shelf carbonate platform (pelletal limestone facies) stromatoporoid association from the late Sheinwoodian of Saaremaa (Baltica) contains a diverse assemblage of sclerobionts (both epi- and endobionts). The studied stromatoporoids vary from low domical to extended domical shapes. Cornulites sp. aff. C. stromatoporoides, Conchicolites sp., Anticalyptraea calyptrata, microconchids, tabulate (Aulopora sp., Catenipora sp. and favositids) and rugose corals, sheet-like trepostome bryozoans, and discoidal crinoid holdfasts encrust the stromatoporoids. The dominant sclerozoans were tabulate and rugose corals, which is significantly different from several analogous Silurian sclerobiont communities. There may have been taxonomic polarity between an upper surface and a cryptic sclerozoan community. Bioerosion occurs as macroborings in 45.5 % of studied (N=22) stromatoporoids. Endobionts were represented by Trypanites and Palaeosabella borings, as well as embedded symbiotic rugose corals and Cornulites stromatoporoides.