Mazon creek is one of the world's Lagerstatten site noted for exquisite fossil preservation, even soft tissue. The fossils are usually in ironstone nodules that were formed due to coverage in mud and the action of bacteria. Over 400 species from at least 130 genera of flora have been identified from Mazon Creek nodules.

Collectors will recognize this Ptychocarpus unitus fern as both large and superb.