A Strange Fossil Unearthed In Illinois During The 1980s Revealed A Prehistoric Arachnid Once Roamed The State Over 308 Million Years Ago
Once upon a time, a prehistoric species of arachnid roamed the Earth in the area we now know as the state of Illinois. The newly discovered arachnid has been named Douglassarachne acanthopada.
It was around a half-inch long and lived over 308 million years ago. It was also unlike any other type of modern or extinct spider, with traits such as legs covered in spikes.
A fossil of the creature was originally unearthed from the Mazon Creek deposit in northeastern Illinois by Bob Masek, a fossil preparer who worked at the Field Museum and the University of Chicago in the 1980s. It is the first and only fossil of its kind.
The Mazon Creek site is famous for its impressive preservation of remains of ancient spiders, sharks, sea scorpions, and more from the Carboniferous period. The fossils are found inside ironstone concretions.
When the rock was cracked open, there was an impression of a spider-like arachnid with eight legs covered in spikes.
At the time, Masek didn’t realize its significance. He passed the fossil on to private collectors David and Sandra Douglass in the 1990s.
They displayed it in the basement of their shop for years before it dawned on them that the fossil could represent an unknown species. They gave it to the Field Museum in 2023.
Over 300 million years ago, many arachnids, including scorpions and spiders, lived in North America.
However, they didn’t look like the spiders we are used to. Back then, spiders were a rare group. The Douglassarachne acanthopada is an extraordinary example of a now-extinct species.
Kimberly Boyles – stock.adobe.com – illustrative purposes only
“Douglassarachne looks rather like a spider or trigonotarbid but has these very long, curved spines on its legs, which are very distinctive and unusual,” Paul Seden, the lead author of the study, said.
“We do not know much else about it, so we cannot place it close to any arachnid group, but it is probably somewhere near spiders and trigonotarbids.”
The spines are believed to have served as a form of defense and were possibly used to catch prey. Douglassarachne is similar to some of the arachnids of today, such as daddy longlegs (harvestmen), striped lynx spiders, and spiny-backed orb-weavers because they all have spines.
However, the spines on the latter creatures are basically just big hairs. The extinct specimen had real spines.
The pattern, segmentation, and slight constriction between the head and abdomen suggest that it may belong in a group with whip spiders and whip scorpions. Unfortunately, the details of its mouth are unclear, so scientists cannot confirm if this is the case.
Half of the concretion will be returned to David and Sandra Douglass, where it will be displayed in their fossil gallery in Evanston, Illinois.
The study was published in the Journal of Paleontology.
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