A ‘distinctive’ creature with large spiky legs roamed what is now Illinois 300 million years ago

Scientists think the spiny legs were for defensive purposes. - Paul Selden/Museum für Naturkunde

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The idea of ​​unexpectedly coming face to face with a spider-like creature is enough to horrify any arachnophobe, let alone encountering one with large, spiky legs.

But that’s exactly what roamed what is currently northeastern Illinois in the late Carboniferous about 300 to 320 million years ago, according to a study published Friday in the Journal of Paleontology.

The newly discovered, long-extinct species is described by the study authors as a “large arachnid” with “distinctive large spines on its legs.” They were unable to place the creature in any known order of arachnids due to the specimen’s lack of mouthparts, which scientists use to classify them.

“In some arachnids you see kind of spiny legs, but we have never seen one that really has those big spines, at least the first parts of the legs. It’s very, very striking,” said Dr. Jason Dunlop, curator of arachnids and centipedes at Berlin’s Museum of Natural History and co-author of the study, told CNN on Friday.

“We looked at it twice and said, ‘What are we looking at here?'”

Expert fossil preparer Bob Masek first discovered the specimen in the 1980s in the fossil deposits preserved at the Mazon Creek Lagerstätte in Illinois. (The German word is a term paleontologists use to describe an exceptional site with many perfectly preserved fossils.) However, it was not until 2023 that it became clear that the specimen was a newly discovered species and fossil collector David Douglass, who had acquired it from Masek, donated it for research.

Researchers then examined and photographed the fossil using a camera attached to a microscope.

They found that the creature was “clearly something quite different from any previously described arachnids,” with spiny legs similar to some modern harvestmen, but with a different body type.

Scientists think the spiny legs were for defensive purposes.  - Paul Selden/Museum für NaturkundeScientists think the spiny legs were for defensive purposes.  - Paul Selden/Museum für Naturkunde

Scientists think the spiny legs were for defensive purposes. – Paul Selden/Museum für Naturkunde

The creature likely used its spines for defensive purposes rather than to attack other animals, similar to a hedgehog’s spines today, Dunlop said.

“It means that if something tries to bite it, it catches the spines in its mouth. … We talk about processing time, which means if you want to eat something with spines, it will take longer because you have to break off the spines or bite the pieces that don’t have spines on them,” he added.

“We can guess that there were scorpions and other spiders in the area,” Dunlop said, as well as primitive lizard-like animals or large amphibians that might have preyed on these arachnids, but we can’t say for sure.

Without the mouthparts, researchers can’t pinpoint its closest relative, but they hypothesize it could belong to a larger group, including spiders, whip spiders and whip scorpions.

Paleontologists have so far only found this particular species in North America, but it could also “emerge elsewhere in Northern Europe,” Dunlop said.

“A huge area across much of what is now Europe and North America was probably some kind of giant tropical rainforest and where coal is found today you have a reasonable chance of finding these fossils (of arachnids, plants and insects) ,” he added.

Researchers eventually named the species Douglassarachne acanthopoda. The genus name honors the Douglass family, who donated the specimen to the Field Museum of Natural History in Chicago, and the species name refers to the spines that make this arachnid so distinctive.

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