The specimens washed up on the beaches of the North Sea are almost certainly fossil (from the Pliocene and the Eemian), as this species no longer occurs in the south-eastern part of the North Sea.
Many species from the Eemian layers nowadays show a much more southern distribution, ranging from South of the Strait of Dover to Portugal (Lusitanian faunal province) and even into the Mediterranean (Mediterranean faunal province).
Eemian |