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
Geology of the North Sea in the West, just North of the Netherlands. A larger graben is found in the subsurface below the Skagerrak, this north-south structure is called the Bamble-Oslo Graben. The Viking Graben is separated from the Faeroe Shetland Basin below the Atlantic by the Shetland Platform, the two structures join in the area north-east of the Shetland Islands. The area we now call the North Sea was interspersed amid several separate continental areas (Siberia, Baltica, Gondwana, and Laurentia) as well as the Iapetus Ocean and Tornquist Sea. Plate tectonics and continental collisions (orogenies) brought the features together of the North Sea that