gryphaea obliquata

Gryphaea is an extinct oyster; it is also a very distinctive one.As a bivalve it posseses two valves. The valves are markedly unequal in size and shape, the left valve is strongly incurved, the right valve is small and flat. The left shell is thick and its surface is marked with numerous ridges.The devil’s toenail found on the Dorset coast is Gryphaea obliquata, it can be distinguished from Gryphaea arcuata as the umbones (beak) of the left valve are more closely incurled in the latter. Gryphaea obliquata is medium sized typically 60mm in length.They lived on the sea floor with the flat right valve facing up, it probably acted like a lid, when open allowing water carrying oxygen and nutrients to flow in and be filtered out of the water.

Gryphaea is a very common fossil around Lyme Regis, it can be found in a number of layers both to the east and west of the town.At low tide the rock platforms below the seawall east of the town become exposed. Look closely at the hard grey-blue limestone beds of the Blue Lias, you will see the outlines of large ammonites. Keep looking for white, strongly curved half-moon shapes often close together.Likewise, to the west at Monmouth Beach they can be seen in the hard limestone beds. However, at a few horizons in the intervening mudstones whole specimens can be found. If you look amongst the pebbles and in the rock pools you may be lucky enough to find a loose specimen.

An iconic fossil for an icon of palaeontology, Mary Anning (1799-1847), now one of the most celebrated pioneers of palaeontology, is usually associated with her famous discoveries of marine reptiles such as Ichthyosaurs and Plesiosaurus and the pterosaur Dimorphodon.Gryphaea obliquata along with Gryphaea arcuata commonly referred to as devil’s toenails, are both found in the Lower Lias (Lower Jurassic) of Britain. They may not be the most obvious choice to associate with Mary, but as one of the most distinctive and abundant fossils of the Lower Lias, Gryphaea was as familiar to her as it is to fossil collectors that scour the beaches at Lyme Regis today.

Mary was the daughter of cabinet maker Richard Anning of Lyme Regis. The Anning’s supplemented their income by selling curiosities as fossils were referred to.In 1811, after her father’s death (in 1810) her brother Joseph found the first Ichthyosaur skeleton which was to be the catalyst for Mary’s career. Later she was befriended by the famous geologist Henry De la Beche, however, it is largely through her relationships with Elizabeth Philpot and Anna Maria Pinney that we know of her life.There are fossils directly attributed to Mary in The Natural History Museum, many other specimens found by Mary are probably in collections such as the Enniskillen Collection also held at the museum.