Scientists Identify the Head of a Giant Millipede-Centipede Hybrid
Experts knew about Arthropleura, but this is the first time scientists have seen its head
Hiya!
I’m not a fan of bugs, but I do my best to rescue, rather than kill, the ones in my home. Still, anything larger than a coin evokes a sharp “nope” response, and I either find a shoe or call for help. So the fact that creepy crawly creatures like millipedes and centipedes were once bigger than me is as terrifying as the idea of being lost in Space.
Yet, hundreds of millions of years ago, such a time did exist, when animals like arthropods grew to enormous sizes — and scientists have the fossils to prove it. Recently, experts identified the head of a giant millipede/centipede hybrid that grew longer than your mattress.
Arthropleura
Considered an arthropod, Arthropleura resembled something akin to a millipede or centipede, except they grew to over 8.5 feet (2.6 meters) long and could weigh over 100 pounds.
According to Amgueddfa Cymru, one of the seven National Museums of Wales, Arthropleura fossils have been found in Belgium, the Czech Republic, Germany, France, and the UK. Sedimentary geologist Neil Davies of Cambridge's Department of Earth Sciences found the largest so far in 2020 on a beach in Northumberland, England.
More common than fossils of the arthropod’s body are fossils of their footprints, of which there were many, considering Arthropleura had at least forty feet. Evidence of their scuttling over damp ground has been found in Canada, Germany, France, Scotland, and The United States.
While most of these locations are more northern today, they were closer to the equator between 346 million and 290 million years ago when the Arthropleura roamed Earth. These giant arthropods lived during the late Paleozoic era when Earth had an abundance of oxygen. Our atmosphere today is around 21 percent oxygen, but when Arthropleua lived, Earth’s atmosphere contained over 26 percent oxygen, sometimes reaching as much as 30 percent.
Even though scientists have known about Arthropleura for a while, only a few fossils have been discovered of its body, which is how paleontologists know it looked like an enormous millipede… or is it a centipede?
Many people, myself included, don’t know the differences between millipedes and centipedes, but I learned they diverged evolutionary lines around 440 million years ago — even before Arthropleura came around.
Yet, without its head, scientists couldn’t determine which species Arthropleura belonged to or any relationship it may have with modern-day millipedes and centipedes. Mickaël Lheritier, a paleontologist at Claude Bernard Lyon 1 University in France, told Sierra Bouchér of Live Science:
"Arthropleura … has been known since the 18th century, over 100 years, and we hadn't found a complete head.”
But the wait is finally over.
Using modern technology, Lheritier and his colleagues identified not one but two fossilized Arthropleura heads among fully intact juvenile specimens embedded in rocks first found in the 1970s at a French coal field known as the Montceau-les-Mines Lagerstätte.
New Discovery in an Old Discovery
For the study, published in Science Advances on October 09, 2024, Lheritier and his team took CT scans of seven fossil specimens identified as Arthropleura from the Autun Museum of Natural History in France.
The scans provided detailed virtual images of the Arthropleura fossils embedded within the rock, which uncovered the heads of two juveniles. Finally, scientists can determine whether the arthropods were closer to modern millipedes or centipedes — or could they?
The scans showed the young arthropods had small mandibles, eyes jutting out from the sides of their heads on stalks, and gently curved antennae. Lheritier explained to Bouchér:
"Now with the completed head, you can see the mandibles, the eyes, and these characteristics can [help us understand] the position of this [creature] in evolution."
The combination of these traits didn’t clarify the long-held mystery, though. If anything, the find added to it.
The young Arthopleura's bodies sported over 40 legs, with two legs per body segment, just like modern millipedes. But their pincer-like mandibles, which CT scans revealed, are more similar to modern-day centipedes.
Yet, despite their pincers, the Arthopleura juveniles lacked predatory structures such as a way to deliver venom or hunt prey like modern centipedes have. Without such structures, Arthrapleura likely ate debris, which is more similar to millipedes.
Further, the stalked eyeballs sticking out from their heads have never been seen in any known millipede or centipede species, of which there are thousands. However, such an evolutionary eyeball design is commonly seen on fully or semi-aquatic animals, such as crustaceans. Lheritier told Bouchér:
“The stalked eyes remain a big mystery, because we don't really know how to explain this.”
Still, since the fossilized heads belong to juvenile Arthopleura, the team wonders whether the eyestalks indicate that they spend time in the water early in life and then lose the stalks in adulthood.
Regardless, paleontologist James Lamsdell at West Virginia University, who was not involved with the study but wrote in an accompanying perspective published in the same journal, told Sierra Bouchér of Live Science:
"These details, together, may appear to leave Arthropleura as much — if not more — a puzzle than before, but the seemingly chimeric nature of Arthropleura is actually important evidence that may help answer a fundamental question regarding the [evolution of these species]."
Ultimately, paleontologists grouped Arthropleura as being most closely related to the millipede family based on their anatomical features. Still, Arthropleura's hybrid features help scientists bridge the evolutionary gaps between arthropod species.
Perspective Shift
Of the countries I’ve traveled to, India by far had the largest bugs — and I had several, shall we say, entertaining encounters with them.
So, if I ever have the opportunity to safely time travel during my lifetime, I can tell you one time I won’t be traveling to — the Paleozoic era. Although, I can’t help but think riding around on the backs of Arthropleura would be a lot of fun, especially if it wasn’t venomous. Okay, maybe I would visit.
You’re reading my free newsletter, Curious Adventure. If you want more, consider subscribing to Curious Life — which you receive sneak peeks of every Monday morning. This newsletter explores a diverse range of topics and further explores this Curious Adventure we call Life.
These articles require several hours, sometimes days, of research, writing, and editing before publication. The subscription fee helps me pay my bills so I can continue providing high-quality content and doing what I love — following my curiosities and sharing what I learn with you.
If you enjoy my work and want to show me support, you can donate to my PalPal. Thank you for reading. I appreciate you.
