Pecopteris Fern Leaf Fossil
This fine speciemn comes from the Mazon Creek deposits of the region near Braidwood, Illinois and rivals 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. This particular nodule, however, comes from Dresden Lakes in Grundy County Illinois. Like the better-known Pit 11 site near Braidwood, Illinois, this location became the site for cooling ponds for a nuclear power plant. The site is well known for the dark coloration that while esthetically pleasing is somewhat harder to photograph. I recently had an opportunity to acquire a collection that was made in the 1950’s. The Pteridophyte (tree fern) Psaronius became a dominant form supplanting the lycopds. The leaf fronds and pinnules of Psaronius were given the form genus designation of Pecopteris, a highly variable form whose classification is still under review. This is a fine large example which fills is enclosing nodule.