1" Fossil Arthropod (Cyclus) Nodule - Illinois

This is a maxillopod crustacean of the species Cyclus americanus that's preserved within a 1" wide ironstone nodule, collected from the Carbondale Formation near Essex, Illinois. These crustaceans are known as Cycloids and were arthropods that resembled crabs. It's believed that they lived in similar environments as modern day crabs and their fossils have been discovered between the Carboniferous and Cretaceous periods.