Baltic Sea as species in 2005 and 2018 respectively, having formerly been confused with more widespread relatives. The tiny Copenhagen cockle ("Parvicardium hauniense"), a rare mussel, is sometimes considered endemic, but has now been recorded in the Mediterranean. However, some consider non-Baltic records to be misidentifications of juvenile lagoon cockles ("Cerastoderma glaucum"). Several widespread marine species have distinctive subpopulations in the Baltic Sea adapted to the low salinity, such as the Baltic Sea forms of the Atlantic herring and lumpsucker, which are smaller than the widespread forms in the North Atlantic. A peculiar feature of the fauna is that it contains a
History of the North Sea Danelaw, carving out his own kingdom. Harthacanute of Denmark and England was the last Viking king to rule over a territory spanning the North Sea. After Harthacanute's death, the kingdom broke apart. With the rise of William the Conqueror the North Sea began to lose its significance as an invasion route. The new order oriented most of England and Scandinavia's trade south, toward the Mediterranean and the Orient. The Baltic Sea became increasingly important for northern Germany and Scandinavia as well as the powerful Hanseatic League began to rise. Though the Hanseatic League was centered in the Baltic, it also