Monday, July 14, 2014

Homoeospira evax brachiopod from the Waldron Shale

Homoeospira evax is a brachiopod that I mistook for Atrypa until I really got down to look at it. This specimen, from the Waldron Shale of Clark County, Indiana (Silurian, Wenlock epoch, Sheinwoodian to Homerian stage), is typical of the species. While it does have the radiating ribs that you see on Atrypa it also has a prominent beak and narrower hinge line. Additionally H. evax does not have concentric growth lines on the surface of it's shell like Atrypa does.

Brachial valve
Pedicle valve

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