A remarkable fossil was recently discovered on a quiet beach in northern England. It reveals a giant millipede, stretching nearly nine feet long! This creature, known as Arthropleura, is now recognized as the largest land invertebrate ever to exist.
Living over 326 million years ago during the Carboniferous period, this massive millipede roamed the Earth long before dinosaurs appeared. The find is significant, not just because of its size, but also because it helps us understand how such large creatures evolved on land.
The fossil was found in Howick Bay, Northumberland, after part of a cliff collapsed. Inside a sandstone boulder, researchers from the University of Cambridge discovered an intact segment of its exoskeleton, leading experts to estimate that the full creature could grow up to 2.7 meters long and weigh around 50 kilograms.
The fragment measures 75 centimeters, but it’s likely just a shed exoskeleton. Comparisons suggest the complete animal was about the size of a compact car. These prehistoric giants thrived in the tropical landscapes of what is now Great Britain, which was near the equator during that period.
Interestingly, prior findings in Germany were smaller and less complete, making this fossil uniquely valuable. Instead of the coal swamps previously thought to be their typical habitat, this fossil was found in what used to be a fossilized river channel, suggesting that Arthropleura thrived in open woodlands near ancient waterways, feeding on decaying plants.
Dr. Neil Davies from the University of Cambridge described the discovery as a “complete fluke.” The fossil’s excavation began in 2018 with the help of Natural England and local landowners. The details and dimensions of the specimen are now documented in the Journal of the Geological Society.
Rethinking Gigantism in Prehistoric Arthropods
For many years, scientists believed high atmospheric oxygen levels were responsible for the gigantic size of Paleozoic arthropods. However, this fossil predates the known peak of oxygen in the late Carboniferous, when levels were only slightly higher than today’s. This challenges the prevailing idea that oxygen was the main factor behind their enormous growth.
Researchers are now looking into various factors for this gigantism. These include abundant plant nutrition, a lack of terrestrial predators, and stable equatorial climates, all of which helped support large invertebrates.
A 2024 study published in Science Advances used CT scans to examine juvenile Arthropleura fossils, shedding light on their anatomy. These scans revealed details about their head structure, including short antennae and internal mandibles, placing them in an extinct group similar to both millipedes and centipedes.
The Decline of Arthropleura
Despite thriving for roughly 45 million years, Arthropleura went extinct during the early Permian period, around 290 million years ago. Climate changes led to drier, more seasonal conditions, reducing their habitat and disrupting their moisture-dependent breeding.
Research suggests that the molting process became riskier as the environment dried up. Large arthropods needed stable, moist conditions for molting—requirements that worsened during Permian desertification. Furthermore, the rise of early reptiles may have introduced competition for resources.
Most known fossils of Arthropleura, like the recent find, are actually molted carapaces rather than complete skeletons. This absence of full body fossils limits our understanding of their behavior and ecology.
A Glimpse into Ancient Ecosystems
This discovery is a reminder that ancient ecosystems were more diverse than we often imagine. The size and existence of Arthropleura indicate a rich environment that supported giant invertebrates—not just in isolated swamps, but across vast open woodlands in equatorial Europe.
Trackway fossils, found in places like Nova Scotia, show that these creatures moved slowly across forest floors, leaving large imprints that help confirm their size, even when complete fossils are lacking.
Now displayed at the Sedgwick Museum of Earth Sciences, the Northumberland fossil offers a fascinating glimpse into a world that once held impressive creatures, reminding us that Earth’s history is full of surprising giants.
