Researchers Confirm Devonian Scorpion Praearcturus gigas as Largest Known Species

A team of paleontologists from the Natural History Museum in the United Kingdom has confirmed that the Early Devonian arthropod Praearcturus gigas was a scorpion measuring more than a metre in length, making it the largest known scorpion in the fossil record. The species, first described from fossils discovered in 1870, was re-examined with modern techniques including camera lucida tracings, computed tomography scans and comparative analysis with other Devonian specimens.

The researchers estimate the animal’s pincers were about 16 cm long, longer than the bodies of many modern scorpions, and note ridged limb surfaces that likely produced sounds through stridulation. Fossil evidence of flap-like epimera suggests the creature may have spent part of its life in water, similar to modern lobsters and crabs.

"Praearcturus lived when life on land was just starting out and the ancestors of reptiles, mammals and birds were yet to leave the water," said lead author Richie Howard.

"It suggests that this species might have grown so big because there weren't any other large predators, allowing it to dominate its environment."

"Without complex ecosystems to support Praearcturus on land, these animals probably spent part of their lives hunting in water," Howard added.

The study also references earlier work on the Canadian scorpion Eramoscorpius to support the classification of P. gigas as a true scorpion. Additional commentary from paleontologist Greg Edgecombe links the findings to broader arachnid evolution, noting that scorpions share respiratory traits with spiders and likely descended from air-breathing ancestors before some returned to aquatic habitats.

Published in the journal Palaeontology, the findings provide new insight into the early colonisation of terrestrial environments by arthropods and help refine timelines for the transition of life from sea to land.