Placophyllia rugosa (Becker 1875)

6.5x3x5cm. Upper Kimmeridgian, Mergelstetten Formation (Malm zeta). Found on a field close to Gerstetten in the area around Nattheim. The Fauna found here is mostly immersed in limestone blocks, but one can release them from their captivity by giving them a bath in diluted hydrochloric acid. The corals have mostly been silicified during the diagenese. This often makes for lovely results if you find the right block, but it's a bit of an investment, so you have to be pretty sure that something interesting is hiding in there.