Megastrophia concava brachiopod from the Jeffersonville formation

Among the largest brachiopods know is Megastrophia concava which is somewhat common in lower to middle Devonian aged rocks.  The shell is typically oval to rectangular in shape, has a convex pedicle valve, a convex brachial valve and a straight hinge line. It is a member of the order Strophomenida and is related to Strophomena, Leptanea, and others with a similar shell morphology.  This specimen is preserved by chert/beekite and only a partial internal/external cast of the pedicle valve is visible.

Pedicle valve

Anterior - most of the edges of the fossil near the margin show the exterior radial ribs.

Right profile

Posterior showing the internal cast where the muscles were attached (triangular shapes). The round bubbly shapes are Beekite which is a form of quartz.

I found this specimen near Lousiville, KY and believe it comes from the Jeffersonville Limestone, dated to the Devonian period (Eifelian stage).