RARE Mamayocaris Mazon Creek Lobster-Like Crustacean Fossil

Mamayocaris jaskoskii

Class Crustacea, Order Pygocephalomorpha

Geological Time: Pennsylvanian (~300 m.y.a.)

Size: Fossil is 35 mm long by 12 mm across (plus antennae), Matrix: 50 mm by 35 mm nodule pair

Fossil Site: Mazon Creek, Goose Lake, Morris, Illinois


Mamayocaris jaskoskiiDescription: The Mazon Creek deposits of the region near Braidwood, Illinois rival the other famous Lagerstatten of the Burgess Shale, Solnhofen, and Liaoning for the variety of detailed life preserved. Many exquisitely-preserved specimens are found in the ironstone nodules that make up the deposits. The majority of collecting areas are the spoil heaps of abandoned coal mines, the most famous of which is Peabody Coal Pit 11. Pit 11 now serves as a cooling pond for the Braidwood nuclear power plant, but with over 100 other localities, specimens still come to light.

This fossil is of a group rarely seen from the Mazon Creek fauna which was thought to have been a bottom-dwelling scavenger. Of several thousand nodules I have seen, this is only the SECOND. This is a finely-detailed part/counterpart example sure to be a cornerstone of any collection from the region.

Also see: Rare and Museum Fossils

click fossil pictures to enlarge


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