Scientists have described the largest known fossil scorpion, which lived about 415 million years ago in what is now the United Kingdom during the Early Devonian period.

The species, named Praearcturus gigas, reached an estimated length of about 1 meter. Its claws could grow to around 16 centimeters, indicating a potential role as an active predator in ancient ecosystems.

At that time, land ecosystems were still at an early stage of developing complexity and were inhabited mainly by small arthropods. It is assumed that P. gigas may have occupied the top positions in the food chain and hunted on floodplains.

The discovery of such a large scorpion from such an early geological period is important for understanding the evolution of gigantism in arthropods and the development of terrestrial ecosystems.

Previously, specimens of Praearcturus gigas were known from finds dating back to the 19th century in England and Wales, but their taxonomic classification remained disputed for a long time. At different times, they were interpreted as crustaceans and later as scorpions, but the absence of key anatomical elements, such as a clearly defined tail section, made definitive classification difficult.

In a new study, the results of which were published in the journal Palaeontology, scientists reexamined museum specimens using modern imaging methods and comparative analysis. The results confirmed that P. gigas most likely belongs to scorpions.

The identification of a number of other specimens from the same geological layers, which were assigned to this species, was also revised.

Researchers suggest that the animal may have had a partially aquatic lifestyle. This is indicated by the presence of structures resembling epimeres—plate-like elements similar to those found in modern crustaceans and serving to protect and support the body.

According to the authors of the study, an aquatic or semi-aquatic environment may have contributed to the animal’s large size by supporting its mass and reducing the limitations typical of a fully terrestrial environment.

Scientists note that the existence of such a large predator at a time when terrestrial ecosystems remained relatively simple points to a more complex and earlier evolution of arthropods than previously thought.