Empty Flat Oyster shells on the beach (1)

This is one of a series of posts about OYSTER VARIATION.

The shells of the European or Flat Oyster (Ostrea edulis Linnaeus) must surely be the most variable in appearance of any bivalved mollusc species. This variability has been a source of fascination for many years. From the ancient Romans to the Victorians, the visible differences have been considered clues to the place of origin for the oysters.

In more recent times, variations in oyster shells that are visible to the naked eye (macroscopic) are being investigated by archaeozoologists for their potential usefulness in understanding how this marine resource was exploited in the past. They are wondering whether variations might indicate the place of origin for the shells and thus pin-point ancient trade routes. They also want to know whether the shells will provide evidence to show if oysters were fished from naturally occurring populations or were the result of some degree of farming or cultivation.

This is the first post on EMPTY FLAT OYSTER SHELLS ON THE BEACH in which the photographs will demonstrate in a general introductory way some of these macroscopic variations in the shells. All the pictures will show the oyster shells in situ just as they were found on the seashore.

Accompanying these posts will be occasional articles in the blog describing in more detail and illustrating aspects of variation such as colour, size, shape, infestation damage, and epibiont encrustation evidence. Several such articles have already been posted:

Colour variation in oyster shells (1);

Flat Oyster shells with Polydora ciliata burrows;

Ancient and modern Polydora ciliata type burrows in Flat Oyster shells

Oyster shells from Studland Bay

Clumped oyster shells (1)

Black oysters at Rhossili Bay

Any investigation to answer the questions posed by archaeologists needs a recognition of the nature of the shell variants; identification and definition of the varying elements; comprehension of the significance of each varying element; quantification of the variations; computation and statistical analysis of the data; and interpretation of the results before any discussion of the findings, and drawing of conclusions.

In summary, individual oyster shells have widely varying visible characteristics. Archaeomalacologists may be able to use the qualitative and quantifiable characteristics in samples of oyster shells from historical deposits to demonstrate spatial and temporal variations useful for archaeological interpretation. Understanding the nature of macroscopic variations in oyster shells from the past requires an examination of more recent specimens.