Imagine a creature with dozens of legs, stretching nearly nine feet long, that once crawled through ancient forests—a monstrous, now-extinct arthropod known as Arthropleura. Despite its massive size and striking appearance, scientists have struggled to piece together what the head of this giant looked like. Most Arthropleura fossils are headless, abandoned shells left behind when the creature molted, shedding its exoskeleton to grow larger. These fossils show a body reaching up to 9 feet in length and weighing over 100 pounds, yet their mysterious head shape remained hidden for decades.
Recently, however, paleontologists uncovered fossils of juvenile Arthropleura that were remarkably well-preserved, including their heads. Studying these intact specimens, scientists were able to finally visualize this ancient predator’s head, which turns out to be as fascinating as it is formidable. According to new research published in Science Advances, the head of Arthropleura sported a rounded bulb shape with crab-like, protruding eyes, short bell-shaped antennae, and a relatively small mouth designed for grinding leaves and bark.
Arthropleura belonged to the arthropod group, a classification that includes modern insects, spiders, and crustaceans. Although resembling a cross between today’s centipedes and millipedes, Arthropleura was uniquely adapted, blending features from both of these groups. Its body resembled that of a millipede, with multiple segments and rows of legs, but its head structure aligned more closely with that of a centipede. According to study co-author Mickael Lheritier, a paleobiologist at the University Claude Bernard Lyon in France, this mix of traits highlights the evolutionary diversity within ancient arthropods.
Though it may be the largest terrestrial arthropod ever discovered, some paleontologists argue that Arthropleura might still fall short of being the largest arthropod overall, as it contends with the extinct giant sea scorpion, another prehistoric predator. Since the late 1800s, researchers in Europe and North America have been collecting fragments and fossilized footprints of Arthropleura, but full specimens—especially with intact heads—remained elusive until now.
The new discovery was made possible through advanced technology. To study these fossils, researchers employed CT scanning on juvenile specimens that had been preserved within rocks from a coal field in France, initially discovered in the 1980s. CT scanning enabled scientists to see delicate details of the head structure hidden within the rock, a critical tool given the risk of damaging such fragile fossils during traditional excavation methods. West Virginia University paleobiologist James Lamsdell, who was not involved in the study, noted that CT scanning “allowed researchers to scrutinize hidden details like bits of the head that are still embedded in the rock.”
The juvenile fossils measured only about 2 inches long, significantly smaller than the massive adults, and might represent a different, smaller type of Arthropleura. However, the researchers believe these specimens are closely related enough to offer a glimpse into the anatomy of their gigantic counterparts, which roamed lush forests approximately 300 million years ago during the Carboniferous period.
Through these findings, we now have a clearer image of Arthropleura’s head and how it may have lived. Although primarily a herbivore, with a mouth adapted to grind plant material, its sheer size would have made it an imposing presence in ancient ecosystems. This new research not only reveals details about one of the largest terrestrial arthropods ever, but also enriches our understanding of the evolutionary history of arthropods, a group that continues to thrive in diverse forms today.