Diverse endobiotic symbiont fauna from the late Katian (Late Ordovician) of Estonia

Endobiotic cornulitids formed symbiotic associations with tabulate corals and stromatoporoids in the Katian (Late Ordovician) of Estonia. The cornulitids benefited from a stable substrate and additional protection against predators offered by the skeleton of their hosts. Symbiotic lingulates and Chaetosalpinx-like bioclaustration structures are here reported from bryozoans for the first time. The endobiotic lingulates were also symbionts of tabulate corals in the Katian of Estonia. Bryozoans hosted the most diverse fauna of endobionts in the Katian of Baltica. Corals and stromatoporoids hosted just few groups of endobionts in the Katian of Baltica.