Brachiopod
Fossil
Found in Ruan, County Clare.
This 320 million years old carboniferous fossil is preserved in limestone. The shell detail is preserved in calcite.
Brachiopoda (from the Latin, brachio: arm, pod: food) are very useful in dating rocks, as they occur in all rocks from the Cambrian to the present, with many diverse and distunguishable species. They resemble the bivalve molluscs and clams, but differ from them in their symmetry: brachipoda shells have the axis of symmetry through the middle of each shell, while bivavles have each shell a mirror image of the other.
Brachiopods are divided into those that have hinges between their valves (articulates) and those which do not (inarticulates). They generally attach themselves to the sediment with a fleshy stalk or pedicle.
Ref: 2000.230
