Productid brachiopod

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The impressions on this pebbly sandstone represent the external castings of productid brachiopods from the Permian Sydney Basin in eastern Australia. Brachiopods, known as "lamp shells," are differentiated from other bivalved organisms such as pelecypods by their two valves that have different shapes and a plane of symmetry perpendicular to the hinge line. Productid brachiopods can be identified by their spines which functioned as anchors in the seafloor sediment. The anchoring spines on this specimen are beautifully preserved (as castings) and appear as small holes within many of the external castings.