Description

Essexella asherae
Early Pennsylvanian
Carbondale Formation
Mazon Creek, IL, USA

1 inch jellyfish in half concretion

Jellyfish, Mazon Creek. Soft-bodied. Cnidarian.

Essexella is a genus of jellyfish, the specimens of which were considered unidentifiable “blobs” prior to its description.  The remarkable preservation allowed within many Mazon Creek concretions reveals a number of Late Carboniferous soft-bodied organisms that would have gone unknown to science without them.  These concretions offer a more complete sample of an ecosystem seldom repeated across the fossil record.