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
Opening of the North Atlantic Ocean Opening of the North Atlantic Ocean The opening of the North Atlantic Ocean is a geological event that occurred over millions of years, during which the supercontinent Pangea broke up. As modern-day Europe (Eurasian plate) and North America (North American Plate) separated during the final breakup of Pangea in the early Cenozoic Era, they formed the North Atlantic Ocean. Geologists believe the breakup occurred either due to primary processes of the Iceland plume or secondary processes of lithospheric extension from plate tectonics. Rocks from the North Atlantic Igneous Province have been found in Greenland, the Irminger Basin, Faroe Islands, Vøring