Fossil Oysters 1

Fossil oyster shell, Deltoideum (Liostrea) delta, paired valves with right valve uppermost.

This Post features one of many fossil oysters that I have picked up on the beach over the years because they were in some way unusual and because of my interest in the variation in oyster shells from both present day populations and from samples of oyster shell from archaeological excavations.

I am particularly interested in the range of sizes, shapes, and the evidence for both encrusting or infesting epibiont organisms. These features reflect the variability in a species which can be a response to the immediate natural environment of the oyster during life and the effect of taphonomic processes (things that happen to the shell after the death of the animal) on the appearance of the shell, whether it be fossil, archaeological or recent in origin.

The paired shells of the oyster in this specimen from Ringstead Bay in Dorset, UK, were still together in situ. There was very little internal space between the right and left valve – as is typical for the species which is Deltoideum (Liostrea) delta. It is a common find in the Kimmeridge Clay of the Jurassic Period that outcrops on the beach. The left valve had another broken oyster shell attached to it externally. This would have been the substrate on which the spat oyster had originally settled.

On opening and separating the two valves, it was possible to examine the hinge or ligament area. The ‘scar’ where the flexible ligament had conected the two shells showed many growth lines indicating some age had been achieved prior to death. Petrified material attached to the ligament scar, fragments on both valves but more noticeable on the left valve, could be the fossilised remains of the ligament itself.

Fossil oyster shell, Deltoideum (Liostrea) delta, paired valves with left valve uppermost.

Fossil oyster shell, Deltoideum (Liostrea) delta, paired shells separated to display the outer surfaces of the right and left valves.

Fossil oyster shell, Deltoideum (Liostrea) delta, paired valves with left and right valves separated to show the inner surfaces.

Fossil oyster shell, Deltoideum (Liostrea) delta, inner surface of left valve displayed.

Fossil oyster shell, Deltoideum (Liostrea) delta, inner surface of left valve displayed with scale.

Fossil oyster shell, Deltoideum (Liostrea) delta, inner surface of left valve showing detail of the ligament scar with growth lines and ?fossilised remnants of ligament itself.

Fossil oyster shell, Deltoideum (Liostrea) delta, inner surface of right valve displayed.

Fossil oyster shell, Deltoideum (Liostrea) delta, inner surface of right valve displayed with scale.

Fossil oyster shell, Deltoideum (Liostrea) delta, inner surface of right valve showing detail of the ligament scar with growth lines and ?fossilised remnants of ligament itself.

Fossil oyster shell, Deltoideum (Liostrea) delta, side view of paired valves with right valve uppermost.

Fossil oyster shell, Deltoideum (Liostrea) delta, side view of paired valves with left valve uppermost.

Fossil oyster shell, Deltoideum (Liostrea) delta, close-up detail of surface texture right valve

COPYRIGHT JESSICA WINDER 2013

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About winderjssc

Jessica Winder has a background in ecological studies in both the museum and the research laboratory. She is passionate about the natural world right on our doorsteps. She is enthusiastic about capturing what she sees through photography and wants to open the eyes of everyone to the beauty and fascination of nature. She is author of 'Jessica's Nature Blog' at http://natureinfocus.wordpress.com. Jessica has also extensively researched macroscopic variations in oyster and other edible marine mollusc shells from archaeological excavations as a means of understanding past exploitation of marine shellfish resources. She is an archaeo-malacological consultant through Oysters etc. and is publishing summaries of her shell research work on the WordPress Blog called 'Oysters etc.' at https://oystersetcetera.wordpress.com 'Photographic Salmagundi' at http://photosalmagundi.wordpress.com is a showcase of photographs and digital art on all sorts of subjects - not just natural history.
This entry was posted in FOSSIL OYSTER SHELLS, Nature, PALAEONTOLOGY and tagged , , , , , , , , , , , , , , , , . Bookmark the permalink.

3 Responses to Fossil Oysters 1

  1. Teresa says:

    I think I may have found ancient oyster shells Im from new orleans we found them in Lafouch were they are dredging I would like to send you pictures to see if you know anyrhing about them

    • winderjssc says:

      Hello, Teresa. Thank you for writing. Please feel free to send me a photograph of your shells and I will help if I can. However, the people who are most likely to be able to help you in an expert way are those with local knowledge of the area where you found the shells. That might be a museum or university department in or near New Orleans.

  2. Pingback: Fossil Oysters 3 | Oysters etc.

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