'Big as a car': Scientists reveal discovery of 326-million-year-old giant millipede fossil

Researchers in Australia have discovered "the first true millipede" – a 3-inch-long creature with 1,306 legs. But that bug doesn't come close to a recently discovered ancestor from more than 300 million years ago, one that scientists in England say was a millipede "as big as a car" at nearly 9 feet long.

The fossil was found on a beach in the city of Northumberland in northern England, according to the report in the peer-reviewed Journal of the Geological Society,

Neil Davies, lead author of the study from the University of Cambridge's Department of Earth Sciences, said finding the fossil "was a complete fluke" because it was discovered in a block of sandstone that fell off a cliff onto the beach in January 2018.

Finding the fossil in a block of sandstone that fell off a cliff in January 2018 "was a complete fluke," researchers said.

"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," Davies said in a statement

Now, nearly four years later, scientists say this is not only the third millipede fossil ever found, but it is the oldest and biggest to ever exist. The millipede, a species named Arthropleura, lived about 326 million years ago, way before dinosaurs were around. It was 8.6 feet long and weighed about 110 pounds.

The giant millipede Arthropleura, seen in this reconstruction, was nearly 9 feet long, as big as a car.

The millipede is bigger than previously discovered ancient sea scorpions, which were long thought to be the biggest invertebrate animal of all time.

"It was an incredibly exciting find, but the fossil is so large it took four of us to carry it up the cliff face," Davies said. 

The Arthropleura was alive for about 45 million years during the Carboniferous Period when the ancient supercontinent Pangea was mostly still intact. During that time period, present-day England was near the equator. The tropical climate allowed invertebrates and early amphibian species to thrive in vegetation surrounded by creeks and rivers.

There are no clear answers to why the species became extinct, but theories suggest warmer climates and the evolution of reptiles and dinosaurs were probable factors.

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Davies said the creature's diet may have played a significant role in its size. There were numerous high-nutrient nuts and seeds around, but the creatures may have been predators, eating other invertebrates and amphibians.

As huge as the fossil is, it's possible the creature could have actually been bigger. Davies said that when these millipedes die, their bodies would break apart. That's why only two other such fossils have been found, both of them in Germany. So the fossil could be only the creature's body.

"We have not yet found a fossilized head, so it’s difficult to know everything about them," he said. 

The fossil will be displayed at the University of Cambridge's Sedgwick Museum in 2022. 

Follow Jordan Mendoza on Twitter: @jordan_mendoza5.