A Rare Find

RARE FINDS – PEN SHELLS

One the pleasures of being on the Nature Coast Marine Group committee is being asked to identify finds people have photographed. Usually there is someone who knows or whom we can ask and we all learn something. Tristan Johnston sent us photos of a sea pen shell he found so we asked member, Wayne King, one of our shell experts. These bivalves are quite rare in our area.

Wayne explained that two species of pen shell are found on the south coast. They are the largest bivalves on our beaches and are called sea pens because they look like bird feathers, quills, that were used as pens. They are also sometimes called razor clams because they lie half buried with their sharp edges up, often among seagrass. A trap for unwary waders.

In Wayne’s photo of the inside of pen shells, the pieces on the right, (found on the same day in 2015 at Meringo,) are the same species and are different to the shell on the left. (from Batemans. Bay). The intact shell on the left shows a groove or median sulcas on the inside of the shell. It divides the nacreous layer in two.

Bicolor Pen Shell, Pinna bicolor.

The right hand shells (pieces) are probably the Tasmanian Razor Shell, Atrina tasmanica. All three shells are worn and fragile. All the U shaped spines have worn off.

Wayne thought Tristan’s shell had more than the usual number of ribs, they were misplaced and its colour was different. The Qld. Museum confirmed that it is the Comb Pen Shell, Atrina (Servatrina) pectinata, but this species has never been found south of Sydney. Is that because no one has looked?

If you photograph some interesting marine finds above or below water, please share them with us.