Giant Devonian scorpion identified from British fossils

A team of paleontologists has re-evaluated fossils held at the Natural History Museum in London and determined that Praearcturus gigas, a creature about one metre long that lived in the early Devonian period, was a scorpion rather than a crustacean. The study, published in the journal Palaeontology, combined CT scans of eight specimens from three sites with comparative analysis of a related Canadian scorpion, Eramoscorpius brucensis, noting identical sternum features.

The researchers estimate the animal’s pincers were roughly 16 cm long and its abdomen bore flap-like lateral epimera, structures more typical of marine arthropods such as horseshoe crabs. These features suggest the scorpion could have swum, supporting the authors’ hypothesis that it led an amphibious existence, preying on early jawless fish rather than solely on small terrestrial arthropods.

"That is a chonky-looking organism," said paleobiologist Russell Bicknell, who was not involved in the study.

"How we think about extinction and evolutionary biology comes from the ability of scientists to work over the same ground, by repetition," said Elizabeth Dowding, chair of paleoenvironmental analysis at Friedrich-Alexander University.

"It’s exactly the same in the two scorpions. So, we can infer from that that these are two closely related animals," said lead author Richard Howard, curator of fossil arthropods.

The classification has implications for paleobiology databases and may prompt further searches for Devonian scorpions. Some experts remain cautious, noting that key scorpion features such as a stinger and pectines have not been observed in the fragmentary fossils.

"Things like big pincers might also be seen in some crustaceans," said Jason Dunlop, scientific director of the arachnid collection at the Museum für Naturkunde in Berlin.

The study highlights the role of revisionary science in reshaping understanding of ancient ecosystems.