2.5" Ordovician Algae? Fossil (Receptaculites) - Minnesota

This is a 2.5" wide example of a Receptaculites fossil from an Ordovician marine deposit in Minnesota. Little is known about these marine fossils aside from that they appeared to be integral to the formation of coral reefs in Ordovician seas. They are believed to be a type of calcareous algae (algae that is hardened from calcium content) and have been found in the fossil record everywhere outside of Antarctica. Overall, a really unique addition to any collection.