Plant Fossils

Medullosa, a Pennsylvanian seed fernOf all the fossils that have been found in Illinois, perhaps none are more famous than the fossil leaves and other plant remains from the world-renowned Mazon Creek-Braidwood area in northeastern Illinois. Fossil hunting is restricted, but permits can be requested from Mazonia Fossil Permit Office, P.O. Box 126, Braceville, IL 60407 or by calling the office at the Mazonia-Braidwood State Fish and Wildlife Area (815) 237-0063. In this area, which lies in Grundy and Will Counties, ironstone nodules containing plant remains are found in waste piles of strip and underground mines and at places along Mazon Creek.

The plant fossils are remains of fast-growing ferns and trees. In the jungle-like growth, the most common plants were huge ferns that had fronds 5 or 6 feet long and grew to a height of more than 50 feet. Along with them were seed ferns, now extinct, and giant scouring rushes, descendants of which are the small horsetail rushes that live today along our wooded streams. Scouring rushes can be recognized by their jointed trunks and the leaf whorls, common in the Mazon Creek nodules. Neuropteris and Pecopteris are from the seed ferns; Annularia is from the rushes. Herbs such as Sphenophyllum formed much of the undergrowth.

The most imposing plants of the Coal Age forests were the scale trees, which grew to heights of 100 feet or more. Close-set leaves grew on their trunks and limbs, and when the leaves fell off, they left rows of scars that are the identifying marks for the trees. Diagonal rows of scars identify Lepidodendron, and vertical rows identify Sigillaria (not shown).

images of plant fossils