Mazon Creek Platysomus Museum Fish Fossil

Platysomus circularis

Order Bobasatriiformes, Family Platysomidae

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

Size (25.4 mm = 1 inch): Fossil is 42 mm long by 22 mm high (as exposed)
Matrix: 63 mm by 55 mm

Fossil Site: Mazon Creek, Braidwood, Illinois

Fossil Code: HMC22

Price: Sold

Platysomus circularisDescription: 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 one comes from Mazon Creek itself. It was found as a single half, and is an example of the fish Platysomus circularis, a member of the Order Bobasatriiformes. Some consider them paleoniscoids while others consider them in their own order as above. The genus had worldwide distribution from the Carboniferous to the Permian. The generic name means wide-bodied and the specific name is of obvious derivation. It is a most uncommon taxon in the Mazon Creek Fauna with only some nine examples known as of 1992. This one has had some preparation to expose more of the fins and tail. If a skilled preparator were employed I believe that even more can be freed from the matrix.

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