Fossils explained 79: Rugose corals

Rugose corals are an extinct group of marine animals that are frequently found in Palaeozoic shallow marine sediments. Just like their counterparts the stony corals (the Scleractinia) do today, during the Palaeozoic the rugose corals were important constructors of reefs. Although at first glance rugose corals look very similar to the Scleractinia, they differ in important details. The rugose corals are a very special group whose relationships have been disputed for a long time. They were restricted to the Palaeozoic Era and experienced an exciting evolutionary history of victories and defeats; there were times when they built up huge reefs (and were valuable in stratigraphy), and other times when they suffered through extinction events.