Ordovician stromatoporoids from the Mjøsa district, Norway

Five species of stromatoporoids are described and illustrated from the Middle Ordovician Mjøsa Limestone of Norway. They include the new genus Radiostroma (type species R. tenue) and three other new species, Labechia bergevikense, Pachysty/ostroma surculum, and P. mammillatum. Radiostroma with its long, slender, flange-like composite pillars, is interpreted as having been derived from a Pachystylostroma-like ancestor. The stromatoporoid assemblage is part of the earliest known stromatoporoid-dominated reef community preserved in European successions.