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Cambridge University Science Magazine

300 million years ago, the world was a strange place. As terrestrial vertebrate life started to diversify, vast expanses of swampland were home to creepy-crawlies the size of modern-day vehicles. A recent fossil of the giant millipede Arthropleura, dating back to around 326 million years ago, reveals this creature as the largest-known land invertebrate of all time.

The fossil, discovered in 2018 in Northumberland and characterised in Cambridge, was found after a large block of sandstone fell and exposed the specimen. It represents the third fossil of this species, but this is the oldest and largest one yet. The 75 cm segment discovered is thought to belong to a creature that spanned 2.7 m and weighed 50 kg, beating the previous record holder the sea scorpion Jaekelopterus.

But how did Arthropleura get to be so large? The most common explanation for the large size of land invertebrates during the Carboniferous, when this giant millipede lived, is that the dense mass of vegetation characteristic of the period released huge amounts of oxygen, which fuelled the growth of large invertebrates. However, the new fossil seems to predate the peak in atmospheric oxygen, so this is unlikely to be the only explanation. Researchers believe that Arthropleura’s diet could also have played a role, but the exact reasons for its size remain unknown.

Adiyant Lamba