Five species of stromatoporoids are described and illustrated from the Middle Ordovician Mjøsa Limestone of Norway. They include the new genus Radiostroma (type speciesR. tenue) and three other new species, Labechia bergevikense, Pachystylostroma 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.
Ordovician stromatoporoids from the Mjøsa district, Norway