Jurassic oysters – Gryphaea

GryphaeaFossilised oyster shells, known as Gryphaea or ‘devil’s toenails’, are common at many locations along the West coast of Scotland. These now-extinct, distinctive bivalves are well-preserved in Lower Jurassic limestone rock formations across the UK, as their thick calcite shells are capable of surviving weathering and erosion. The oysters are labelled ‘devil’s toenails’ because of their ridged, curved, hook-like appearance.

Gryphaea lived in large colonies in warm shallow seas, on the sea-floor with their shells half-buried in the mud. Their shells consist of two parts: a large, hooked lower shell and a flatter, smaller shell on top. The soft parts of the animal were enclosed and protected inside the bivalve shell, the same as modern oysters. Particularly good examples can be found on the shoreline at Lochaline, in the Lochaber Geopark, where they are washed up by the sea, and at Waterloo, Broadford on Skye. These fossils are an excellent ‘starter fossil’ for children to collect, because they are easily recognisable and often found in abundance.