Actinian dominated intertidal mudflats: A new case of an extraordinary rare phenomenon from Southern Chile

► A macrobenthic community dominated by an intertidal sea anemone is described. ► The population occupies about half of the total area of the tidal flat. ► Anthopleura hermaphroditica is native to the Pacific coast of Chile. ► For more than 20 years, the population has been stable and its density high.