The remains of the largest scorpion in history have been found in Britain

It's a species called Praearcturus gigas. Its fossils have been known for more than a century, but scientists have long debated whether the animal was a giant crustacean like a midge or a scorpion.

A new study in the journal Palaeontology supports the second version.

It's not a fully preserved scorpion from head to tail. It's about body fragments that have been reexamined using modern methods. But these data were enough to classify the animal as a scorpion and estimate its enormous size.

Details

Fossils of Praearcturus gigas were found in Early Devonian sediments in what is now England and Wales. The species was first described by Henry Woodward back in 1871. At that time it was recognised as a large crustacean, similar to a midge. Even the name Praearcturus is related to Arcturus, a group of modern marine crustaceans.

Later another version appeared: perhaps it was not a crustacean, but a giant scorpion. But it was difficult to prove it, because only some parts of the body were preserved, and the characteristic scorpion tail was not among them.

In the new work, the researchers re-described the old and new fragments. They used drawings, conventional photography and tomographic data - essentially layer-by-layer images of the fossils. The scientists found several features that support the belonging of Praearcturus gigas to scorpions: large pedipalps with fixed and mobile "finger" claws, a special structure of the sternum and other details of anatomy.

The size of the animal is impressive. According to estimates of the Natural History Museum in London, the claws of Praearcturus reached about 16 cm, and the total body length was more than a metre. By comparison, the largest modern scorpions grow to about 23cm.

This scorpion lived in the early Devonian, when life on land was just starting to become more complex. Plants were small, forests didn't yet exist, and the ancestors of reptiles, mammals and birds were still in the water. Against this backdrop, the metre-long scorpion was a giant.

But it shouldn't be thought of as a land monster. The authors believe that Praearcturus gigas may have been an aquatic or semi-aquatic animal. Its fossils are associated with river environments, and some of its body features resemble structures that help it live in water. It was probably able to hunt both on land and in water.

Its prey could have been small arthropods on land and fish or other animals in the water. At that time, there were few large land predators, so such a scorpion could have had a very important place in the ecosystem.

Why it's important

The find is important not only because of its size. It shows that large predators appeared very early in the history of land exploration by animals.

Usually when we talk about giant arthropods, we think of huge millipedes like Arthropleura or the giant dragonfly-like insects of the Carboniferous period. But they lived at least tens of millions of years later. Praearcturus gigas existed much earlier - at a time when terrestrial ecosystems were still emerging.

This helps us understand how animals moved between water and land. Scorpions today are terrestrial predators, but their ancient history may have been more complex. If Praearcturus was indeed semi-aquatic, it means that early scorpions could use both environments and did not immediately become completely terrestrial.

Background

Scorpions belong to the arthropods, a huge group of animals that includes insects, spiders, crustaceans, millipedes, and many others. Arthropods have an external skeleton, articulated limbs, and a segmented body.

On land, the size of these animals is usually limited: it is more difficult for them to support their bodies and breathe when they are large. In water, large arthropods have an easier time because the water supports their body mass. So the idea that the metre-long scorpion could have been at least partly aquatic seems logical.

The peculiarity of Praearcturus gigas is that it lived at the border of two worlds - when animals had already begun to master the land, but many large forms were still dependent on water.

Source

Study: Richard J. Howard et al., "A revision of Praearcturus gigas: a giant scorpion from the Lower Devonian (Lochkovian) of Britain", Palaeontology, 2026.