This Ancient, Nine-Foot-Long, 100-Pound Millipede Could Be the Largest Invertebrate to Ever Live

An illustration fo the millipede crawling on a sandy bank. It has black, segmented body resembling armor. It scuttles across the sand, with a river and vegetation around it.
Arthropleura skittered around the Earth during a time when England was located near the equator and experienced tropical weather. Neil Davies

Scientists just discovered a terrifying nearly nine-foot-long, 110 pound millipede that scurried across the ground around 326 million years ago, according to a study published in the Journal of the Geological Society this week. It could be the “biggest bug that ever lived,” unseating sea scorpions as the previous record-holder, Katie Hunt reports for CNN.

In 2018, a group of scientists on a trip to Northumberland—a county in northeast England—discovered the fossil when a giant sandstone rock fell off a cliff and crashed onto the beach, Harry Baker reports for Live Science.

“It was a complete fluke of a discovery,” lead author Neil Davies, a geologist at the University of Cambridge, says in a statement. “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.”

Upon analysis, the scientists found that the rock contained about a 30-inch segment of the fossil, though the animal would’ve been more than three times that size. They determined that the critter belonged to the long-gone genus Arthropleura, David Nield reports for Science Alert.

A photo of the rock containing the fossil. The rock is gray and brown, and it contains scale-like imprints of the millipede's exoskeleton.
The rock contained about a 30-inch segment of the fossil, though the animal would’ve been more than three times that size. Neil Davies

“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 molted carapace that the animal shed as it grew,” Davies says in the statement. “We have not yet found a fossilized head, so it’s difficult to know everything about them.”

For example, the team can’t definitively determine how many legs the millipede had, but they estimate it had either 32 or 64, Hannah Seo reports for Popular Science.

Arthropleura skittered around the Earth for around 45 million years during the Carboniferous Period, a time when England was located near the equator and experienced tropical weather. The millipede’s monstrous size may have been partly due to a high concentration of atmospheric oxygen, but it’s more likely that a diet of nuts, seeds and possibly other animals boosted its growth spurt, according to the statement.

However, the genus went extinct curing the Permian period, possibly due to changes in the climate or the emergence of reptiles, which may have beat out the leggy critters, CNN reports.

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