Studying A Fossilized Fern

 By Wyatt Maeder

The fossilized fern pictured in this paper (Figure 1) was found in the famous Mazon Creek fossil beds near Morris in Grundy County, Illinois. Paleontologists have identified this specific specimen as Ptychocarpus unitus. These renowned fossil beds have been actively studied since the middle of the nineteenth century.

Together, the matrix and fossil weigh 14 grams (0.5 ounces). The fossil and its surrounding matrix measure 3 centimeters (1.2 inches) in length. The fossil itself is 1 centimeter (0.4 inches) wide, while the matrix is slightly over 2 centimeters (0.8 inches) wide. This specimen is estimated to have formed during the mid-Pennsylvanian, roughly 309 million years ago.

Figure 1. Ptychocarpus unitus is an extinct fossil fern from the Pennsylvanian Period, preserved in the Mazon Creek Fossil Beds Photo date 2026 by Wyatt Maeder.

As you can see in figure 1 the fern fossil and matrix are a reddish-brown color. This means it is preserved in an ironstone concretion. Some studies show that there could be traces of organic carbon. I do not know this because I don’t have access to a gas spectrometer. 

 

Table. 1 Identification
Taxon:	Ptychocarpus unitus
Family:	Marattiaceae
Locality:	Mazon Creek, IL
Time Period:
Era	Paleozoic
Period	Middle Pennsylvanian

Thanks to exceptional preservation like that found in this fern, scientists can reconstruct ancient equatorial ecosystems, helping us learn more about late Paleozoic plant life, climate, and evolutionary history.

References

Hoskins, J. H. (1933). A Ptychocarpus Type of Fructification from Illinois. The American Midland Naturalist, 14(6), 726–728. https://doi.org/10.2307/2420131

Jennings, J. R., & Millay, M. A. (1979). Morphology of the fertile Pecopteris unita from the Middle Pennsylvanian of Illinois. Palaeontographica Abteilung B, 170(1-3), 51–65.

Tripp, M., Schwark, L., Brocks, J. J., Mayer, P., Whiteside, H. J., Rickard, W., Greenwood, P. F., & Grice, K. (2023). Rapid encapsulation of true ferns and arborane/fernane compounds fossilized in siderite concretions supports analytical distinction of plant fossils. Scientific Reports, 13(1), Article 19851. https://doi.org/10.1038/s41598-023-47009-8

About the author: Wyatt Maeder is a member of the Grand Traverse Area Rock and Mineral Club’s pebble pups. He is 11 years old and in 6th grade.

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