Dwarf cornulitid tubeworms from the Hirnantian (Late Ordovician) of Estonia

Four species of Conchicolites and two species of Cornulites occur in the Hirnantian of Estonia. Two new cornulitids Conchicolites corbalengus sp. nov. and Cornulites levigatus sp. nov. have been described from the Siuge Member. This Hirnantian cornulitid tubeworm association is dominated by species of Conchicolites. Most likely, the studied tubeworms represent true dwarf forms among the cornulitids. It is possible that local waters above the organic rich mud on the seafloor were especially rich in nutrients and allowed cornulitid tubeworms to flourish. The Hirnantian fauna of small cornulitids resembles very much that of late Katian of Estonia and shows no decline in the diversity. It appears that the Late Ordovician mass extinction did not immediately affect small cornulitids, if it did at all.