Unusual Mazon Creek Bristlecage Polychaete Worm Fossil

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. The Polychaeta (Bristleworms) have a diverse representation among Mazon Creek specimens. The segmented bodies of the Polychaeta have paired lobes called parapodia which have a function in locomotion or respiration. The parapodia bear numerous bristles which are the source of the name of the class (Polychaeta means many bristles). This one is what is known as a Bristlecage Worm, a term derived from the long setae surrounding the head. The worm used these to filter diatoms, radiolarian, and foraminifers from the water.