A team of paleontologists has described a shockingly large millipede fossil that was found on an English beach in 2018. The millipede that left the fossil was well over 8 feet long and may have been a predator.
Sometime between April 2017 and January 2018, a large block of sandstone broke away from a cliffside in Northumbria, England, and fell about 20 feet to the beach below. A paleontologist making a serendipitous stroll along the beach found the rock and realized that it contained the fossil of a giant millipede. A team from the University of Cambridge studied the find; their results were published today in the Journal of the Geological Society.
“It was a complete fluke of a discovery,” said Neil Davies, a paleontologist at the University of Cambridge and the study’s lead author, in a university 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.”
The creature is part of the genus Arthropleura, and it lived about 326 million years ago, 100 million years before the first dinosaurs started appearing. The fossil is missing the head, but the animal was estimated to measure 8 feet and 7 inches long and may have weighed over 100 pounds in life.
“These would have been the biggest animals on land in the Carboniferous,” Davies told Gizmodo in an email. “It took four of us with sledgehammers and a pneumatic drill to get it out, and then it was a difficult climb up a 20-metre cliff, carrying the 40 kg fossil between us.”
The research team thinks the fossil isn’t the animal itself but a molted carapace, called the exuvium. So even the size of the animal as it is known from this fossil may not be the largest that millipede eventually grew.
Based on the location of the fossil and stone it was in, the researchers think the exoskeleton was in a river channel, where it was filled with sandy sediment, preserving it. The exoskeleton was found near tetrapod prints dating to the same time, indicating that giant invertebrates coexisted with vertebrates.
The sandstone block also included some fossilized plants from the Carboniferous Period that suggested the giant millipede lived in a drier, more open environment than previously thought. The traditional view has been that arthropleurids lived in swampy environments, since so many of their fossils have been found in coal mines that were once dense, wet forests.
The animals may have gotten so large in part because of how much oxygen was in Earth’s atmosphere in the ancient past. But the Arthropleura predates the peak of that atmospheric oxygen, so there were probably other factors at play, like the animal’s diet. Davies said that the animals may have been predators that got their nutrients from other invertebrates or even amphibians, if not from the leaf litter itself.
These millipedes are now extinct, which may have to do with how the ancient climate changed. “The organisms lived near the equator, which became hot and dry during the Permian,” Davies said. “This likely changed the vegetation and food may have become more scarce. At the same time, the first reptiles were beginning to dominate land habitats, so they would have faced more competition for fewer resources.”
Regardless of the source of their gigantism, the millipedes would’ve been a sight to behold. I, for one, am perfectly happy to admire the creativity of evolution while being grateful I don’t have to see one of these things in the flesh.