IMMENSE Mazon Creek Chondrichthyan Egg Case

Description: 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 particular example comes from Mazon Creek itself. When first discovered over 150 years ago, specimens such as these were thought to be plants. During the 1970’s, examples from Oklahoma were designated as egg cases, most probably those of sharks. Fine spiral markings cover the body of the cases; where they have been compressed, they come through as a crosshatched appearance. Mutiple examples have sometimes been found attached to plant remains much like the spokes on a wheel. This is by far the largest example I have ever had, nearly DOUBLE the usual size.