Crinoid

Scyphocrinites sp.

• Devonian
• Rockhouse Shale
• Hardin County, Tennessee, USA

Size: 12 cm across

This type of fossil was initially described as a crinoid known as Camarocrinus ulrichi. Eventually (and presumably after the well-preserved Moroccan Scyphocrinites were found highly associated with similar structures), it was re-evaluated as being a Scyphocrinites crinoid's lobolith, which is a float-like holdfast that would fill will gas and suspend the crinoid upside down in the water to live a drifting, pseudoplanktonic lifestyle. This particular specimen is from the Devonian instead of the Silurian, so evidently Scyphocrinites also occurs in the Devonian of the USA, though I have not yet looked into the literature.