Giant Scorpion Fossil Confirms Largest Species Ever Lived, Reaching Over a Meter

Scientists have identified the largest scorpion known to have ever lived, a creature named Praearcturus gigas that roamed the Earth approximately 415 million years ago. This ancient arachnid could grow to be over a meter long, roughly the size of a large rabbit or a malabar squirrel.

First discovered in the 1870s in Herefordshire, England, the fossil fragments of P. gigas remained a mystery for over 150 years. Researchers initially debated whether the remains belonged to a giant woodlouse or a large, millipede-like creature. While some studies in the 1980s suggested it might be a scorpion, conclusive proof was lacking.

To solve this puzzle, paleobiologist Richard Howard from the Natural History Museum in London and his colleagues meticulously photographed the fossils and created detailed illustrations. By comparing these images with records of ancient crustaceans and other arthropods, they analyzed preserved structures to confirm the species' identity.

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The mobile claw of P. gigas pointed in the opposite direction to the fixed one, as occurs in modern scorpions.

A crucial piece of evidence came from the shape of the claw. The mobile part of P. gigas's claw pointed in the opposite direction to the fixed part, a characteristic found in modern scorpions but not in crustaceans like lobsters, where the mobile part faces the fixed one. The species also possessed ridges on its pedipalps, appendages ending in claws, which are used by some modern scorpions to produce a hissing sound to deter predators.

Further supporting evidence emerged from comparisons with Eramoscorpius brucensis, a scorpion discovered in 2015 that lived about 430 million years ago. Both ancient species shared an elongated, almost triangular sternum with a central groove, unlike the small, pentagonal sternum found in most modern scorpions. This research also indicates that scorpions achieved extraordinary sizes much earlier than other arthropods, with giant insects not appearing until the Carboniferous period, at least 55 million years later.

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This reference proved key to confirming that P. gigas was a scorpion.