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 southern North Sea Caledonians slowly phase into the Variscan orogeny. The break up of Pangea occurs during the Kimmerian tectonic phase for most of the Mesozoic, until the early-mid Cretaceous, this marks the start of creating the present position of our continents today. During the Jurassic, rifting activity reaches its maximum and North America starts to move apart from Eurasia following that event in the Cretaceous the southern part of North America starts to open up the Atlantic Ocean with the separation of South America and Africa. At the end of the Mesozoic the North Sea reached its final position where it lies