280,000,000 years ago, northeastern Illinois was home to a tropical swamp. Today, the area known as Mazon Creek is frequented by collectors who search for fossil remnants of this diverse ecosystem.

This area is home to many fossils which have been perserved in ironstone nodules. These nodules contain the remnants of prehistoric plants and animals that once lived in the area. The unique flooding conditions of Mazon Creek allowed the perfect enviroment for capturing rare soft-bodied fossils, such as delicate leaves and stems.

This fossil is a large imprint of a Carboniferous era plant which was recovered at the Mazon Creek formation. The plants found here are over 300,000,000 years old and show excellent detail in their preservation.

Each fossil comes shipped in a sturdy carton along with a certificate of authenticity and a small photo card. You can see all our available fossil ferns in the collection below.

“While fossils from Africa, Europe, Australia, and India delight our eye [...], none approaches so closely to that parting of the ways as the tiny creatures found on the banks of Mazon Creek, in Illinois.“ -Paleontologist Roy L. Moodie

At Mazon Creek in Illinois, collectors gather to search the riverside for ancient stones that hold a portal to another world. 300 million years ago, this place was a site where land met the sea and a Paleozoic delta played host to all forms of life and evolution. The creatures that lived here were caught in powerful floods, bringing loads of sediment to cement them in time and preserve them for fossilization. Now, after eons, these fossils are lying in wait ready to be cracked open and explored.

The information gathered by the study of Mazon Creek is invaluable. The location’s prolific fossil beds were discovered in the mid 1800s, and since that time over 400 species of prehistoric plants and 320 species of animals have been identified. These animals have been split into two categories: the marine Essex species and the freshwater Braidwood species. Ocean fossils include jellyfish, clams, shrimp, and fish while the Braidwood species contain insects, arachnids, freshwater fish, and even proto-amphibians.

Fossils were first identified at Mazon Creek in the 1850s. At the time, Mazon Creek was a coal digging site, and amateurs would dig through “spoil piles”—piles of dirt and rock waste produced by mining extraction. Inside, these diggers would find concretions housing fossilized ferns and other plants.

The Carboniferous Period lasted from around 350 to 300 million years ago and is the source of many coal deposits in the modern day. This time was marked by a warm climate and a boom of plant and animal life across Earth's landmasses. Lush forests, massive insects, and even early reptiles were common finds.

Of the several hundred confirmed species identified at Mazon Creek, the majority are ferns. Ferns are vascular plants, defined by their complex tissue system that effectively distributes water and photosynthesis-produced compounds throughout the plant.

Some of the commonly identified ferns include Pecopteris subcrenulata (Lesquereux), which grew into large fronds with a pattern of straight and alternate lateral vein system. Another commonly identified species is Laveineopteris rarinervis (Bunbury) Cleal, with its uniquely dense system of veins making it easy to spot. 

Given the vast diversity of plant life at Mazon Creek, scientists rely on small variations in things like vein systems and leaf pattern to be able to distinguish the many plants from each other. It’s a reminder of just how diverse the ecosystem at Mazon Creek was, and how invaluable a resource it remains today.

What makes Mazon Creek uniquely interesting to paleontologists is the detail in which soft-bodied organisms like jellyfish and insects have been preserved. Since soft tissues are removed by scavengers and decomposition occurs before fossilization, plus jellyfish and insects lack tough bones and teeth, information about these animals is sparse. However, at Mazon Creek, rapid flood cycles deposited large amounts of sediments at once. This covered the creatures bodies and allowed the organic material to convert to fossils.

After the organic material was covered, some bacteria were still able to consume pieces. This decomposition would end up being helpful to the fossilization process though, as it gave off carbon dioxide that mixed with the iron-rich groundwater in the delta. Over time, this would produce concretions of tough ironstone around the fossil, encasing them in a protective bubble without much compression. Because of this, some of the fossils recovered from Mazon Creek form without compression, casting them in three dimensional space.

The steps of this process can be seen in the graphic shown:

a) Creature is deposited in sediment.

b) Bacterial decomposition produces CO2 mixing with groundwater to form the ironstone siderite.

c) Ironstone formation grows into a concretion which protects the fossil.

d) The fossil of the organism is sealed within the concretion and waits for millions of years before being found by paleontologists.