Marine / Estuarine Shrimp: Fossil shrimp were first reported from the Mazon Creek area around 1860, but prior to the opening of Pit 11 in the mid-1950s, the diversity was remarkably small. Now, they are divided into robust non-marine and marine-estuarine groups. These fossil arthropods are preserved in full-body detail or as exoskeleton molts.
Syncarid Shrimp: These are moderately sized crustaceans originally found along the Mazon River. Syncarids lived in fresh or brackish water. They were thought to be extinct until the discovery of living syncarid shrimp in mountain pools of Tasmania in 1893.
Other Essex Biota Crustaceans:
1. Mamayocaris jaskowskii is a moderate-sized crayfish-like animal, probably a scavenger or low-level carnivore, and is a member of the marine Essex Biota.
2. Cyclus americanus – Cycloids are an extinct group whose features are not yet fully understood. They likely filled a crab-like niche in the Paleozoic and are possibly related to Copepod crustaceans.