Chlamys islandica

The Icelandic scallop (Chlamys islandica) is a subarctic bivalve species currently distributed in cold waters around Iceland, Norway, and the North Atlantic. During glacial and post-glacial periods, this species was part of the marine fauna in British waters, thriving in colder climatic conditions. However, as the climate gradually warmed during the Holocene, C. islandica became locally extinct in the region.

It is known from the UK as subfossils—an intermediate state of preservation between recent and fossilised remains. Subfossils retain a significant proportion of their original composition, in this case, calcium carbonate, which slows the mineralisation process typical of complete fossilisation.

The shells likely date to the Pleistocene epoch (2.6 million to 12,000 years ago), though a possible Pliocene origin (up to 5.3 million years ago) cannot be ruled out. It provides evidence of the species' historical range and its response to climatic shifts over geological time. Such findings underscore the profound impact of natural climate change on marine biodiversity and serve as a baseline for understanding more rapid ecological changes occurring today.