Crinoids found as non-native rafters on beached fishing gear in the Netherlands (1936-1951) before the Plasticene

Seven samples of juvenile Antedon bifida (Pennant, 1777) were collected at five localities along the North Sea beach of the Netherlands from January 1936 to December 1951. This crinoid echinoderm is not native to the Netherlands and naturally occurs on rocky substrates ranging from the Shetland Islands to the Canary Islands and the western Mediterranean. The samples were found on bunches of cork fishing floats that had washed ashore. The specimens were deposited in the echinoderm collections of two museum, where they were rediscovered recently. They represent the first records of rafting crinoids on marine anthropogenic litter and predate the Plasticene, which started in the 1950s when plastic started to replace many other materials. Museum collections may still contain undiscovered specimens of non-native species found before their first recorded introduction, potentially shifting baselines back in time.