Club Mosses and their Mighty Ancestors

Like ferns, club mosses are seedless plants, which means they reproduce by releasing a large number of extremely tiny spores. In some species, the spores are released from club-shaped structures that give the plants their nickname (visible on the specimen above). These long-lived evergreen plants are native to moist woodland habitats throughout North America. You might encounter them on a hike if you look low and pay attention to their short, upright stems emerging from the leaf litter.

Some club mosses go by the common name “ground pine” because they resemble miniature conifer trees with their scaly or needle-like leaves. It’s an interesting coincidence because the ancient relatives of club mosses were enormous tree-like plants that dominated swampy forests millions of years before modern trees ever evolved. The forests of the Carboniferous period 300 million years ago would have looked very alien to us. Let’s set the scene. Enormous ferns and horsetails fill the wet primeval forest. The air hums with the sound of a gigantic dragonfly with a wingspan as long as your arm. The tallest trees around are over one-hundred feet tall, with a curious bark texture that looks like a reptile’s scales. This “scale tree” is the titanic prehistoric cousin of our little club moss. The fossils of these extinct Lycophytes and their fellow swamp dwellers are found abundantly at a world-famous paleontological site near Chicago called Mazon Creek.

Mazon Creek is known for its exceptionally well-preserved fossils. Multiple climatic and geological factors in this ancient environment combined to create conditions ideal for preservation. Typically when organisms die, they decay rapidly from exposure to air, bacteria, and fungi, leaving no permanent trace. At this site, however, the habitat was buried suddenly and completely, encasing everything in sediment and preserving plants and more in the fossil record. The Academy’s paleontology collection includes a large selection of Mazon Creek fossils, including fragments of the giant Lycophytes. Our botany collection contains multiple specimens of modern Lycophytes, the club mosses. Natural history collections give scientists the ability to closely study the anatomy of living and extinct species to discover details about their evolution and relationships. This way, all life on Earth can be organized into a big hierarchical family tree called a taxonomy. Life’s taxonomy is not finished, nor is it written in stone. It’s a puzzle with missing pieces. As scientists discover more through anatomical and genetic studies, they often revise the taxonomy by renaming species and reorganizing their relationships in the family tree.

The two fossil specimens above show examples of the bark texture that gave scale trees their nickname. The individual scales are actually scars called leaf cushions – they mark the points where leaves once grew from the trunk. An immature scale tree might have looked a little like an oversized club moss: a straight unbranched column with leaves growing out from the stem. Eventually, the trunk would shed its leaves and the top of the tree would branch off and divide into many leafy twigs, looking more like a typical, modern tree.

These specimens are the fossilized twigs of an extinct Lycophyte. These are small and look quite similar to some living club mosses. However, these are likely just the tips of a much larger tree.

Both living and extinct Lycophytes have important economic uses for humans. Club Mosses have been used for a variety of medicinal and therapeutic purposes for centuries. The remains of extinct Lycophytes, like giant scale trees, are burned for energy in the form of coal. Coal is a result of ancient plant matter being buried under immense pressure by sedimentary rock. Most major coal deposits are the remains of Carboniferous age swamps, which gives them the nickname “coal forests.” Mazon Creek is not just a fossil site, it is also the site of former coal mines. In fact, many of the fossils collected there were originally excavated and discarded as miners dug through the fossil-rich rocks to access the layers of coal below.

Lycophytes, the club mosses, and their extinct cousins, might be easily overlooked when you consider all the other interesting specimens in the museum. However, you’ll find that even the most obscure and diminutive details in nature have epic stories to tell if you give them a chance.

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Encyclopædia Britannica, inc. (n.d.). Lycophyte. Encyclopædia Britannica. Retrieved November 16, 2022, from https://www.britannica.com/plant/lycophyte

Fossil Lycophytes. Sam Noble Museum. (2018, January 30). Retrieved November 16, 2022, from https://samnoblemuseum.ou.edu/common-fossils-of-oklahoma/plant-fossils/fossils-by-plant-group/fossil-lycophytes/

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Lobstein, M. (2020, October 21). Clubmosses: An ancient and interesting group of “Fern allies”. Prince William Wildflower Society. Retrieved November 16, 2022, from https://vnps.org/princewilliamwildflowersociety/botanizing-with-marion/clubmosses-an-ancient-and-interesting-group-of-fern-allies/#:~:text=Club%20moss%20spores%20and%20teas,and%20inducing%20labor%20in%20pregnancy

Wittry, J. (2020). A comprehensive guide to the fossil flora of Mazon Creek. Earth Science Club of Northern Illinois (ESCONI).