Essexella asherae
Pennsylvanian
Francis Creek Shale
Pit 11, Will Co.
Illinois, USA.

For many years, Essexella asherae was interpreted as a type of jellyfish because of its circular body shape and radiating structures. More recent research suggests it was probably a sea anemone-like cnidarian rather than a true jellyfish.
Big 78mm in 110mm paired concretion. One of the larger ones we have had.