Mazon Creek Fossil Fauna
The richness of Mazon Creek fish is due, in part, to the diverse types of environments represented, including coal swamps, deltas, and brackish marine habitats. A large number of genera are attributed to the Essex Fauna which includes such rare forms as lampreys and other jawless fish, in addition to several sharks known only from Pit 11.
Acanthodes beecheri, K.R., Braidwood, IL 2020.
Isolated parts of larger fish such as scales, teeth, bones, cartilage, and skin, occur in the Mazon Creek Fauna and in some cases are the only fossil evidence of a species.