Fossil of largest-ever millipede discovered in England

Researchers say Arthropleura is the largest arthropod in earth's history. The creature is estimated to have been 2.63 metres long and 55 centimetres wide, while weighing 50 kilograms. (Neil Daves)

Vancouver — Geologists in northern England have discovered the fossil of the largest-ever millipede in earth's history.

The creature -- called Arthropleura -- roamed Britain during the Carboniferous Period about 326 million years ago. Researchers estimate the creature would have been nearly three metres long when it was alive.

The researchers outlined their findings in a paper published in the Journal of the Geological Society on Tuesday. The fossil was first discovered in January 2018 after a block of sandstone fell from a cliff in Northumberland, England.

"It was a complete fluke of a discovery,” lead author Neil Davies said in a news release. "The way the boulder had fallen, it had cracked open and perfectly exposed the fossil, which one of our former PhD students happened to spot when walking by.”

Researchers say Arthropleura is the largest arthropod in earth's history. The creature is estimated to have been 2.63 metres long and 55 centimetres wide, while weighing 50 kilograms.

It's also the third fossil of its kind. The other two Arthropleura fossils are both from Germany and are much smaller than the fossil segment found in England, which is 75 centimetres long.

“Finding these giant millipede fossils is rare, because once they died, their bodies tend to disarticulate, so it’s likely that the fossil is a moulted carapace that the animal shed as it grew,” said Davies.

Back in the Carboniferous period, Great Britain would've been located near the equator. The high levels of atmospheric oxygen during this period have been attributed to Arthropleura's large size.

The researchers say it's unclear what Arthropleura may have eaten, but they believe that the creature must've had a high-nutrient diet to reach such a large size.

“While we can’t know for sure what they ate, there were plenty of nutritious nuts and seeds available in the leaf litter at the time, and they may even have been predators that fed off other invertebrates and even small vertebrates such as amphibians,” said Davies.

Arthropleura went extinct during the Permian period between 252 to 298 million years ago. The causes of extinction are also unclear, but researchers speculate that it may have been due to climate change or competition for food from reptiles.