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Arthropods—organisms with hard exoskeletons—compose roughly 75% of all animal species on Earth, ranging from spiders and insects to crustaceans and millipedes.
While many modern arthropods are familiar and often harmless, the prehistoric world hosted creatures far beyond the size of any living relative.
One such marvel is Arthropleura, a giant millipede‑like arthropod that once roamed the terrestrial landscapes of North America and Europe.
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First described by scientists in the United Kingdom in 1854, Arthropleura measured up to 8.5 feet (≈2.6 meters) in length and weighed over 100 pounds (≈45 kilograms). Its colossal size is attributed to the high atmospheric oxygen concentrations that prevailed 290–346 million years ago during the Late Carboniferous.
Despite its impressive size, the creature’s biology remained shrouded in mystery for more than a century because early fossils lacked a complete head, leaving key anatomical features unresolved.
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In 2024, two exceptionally preserved specimens from Montceau‑les‑Mines, France, were scanned using X‑ray micro‑computed tomography coupled with synchrotron imaging. The scans produced detailed 3‑D reconstructions that, for the first time, displayed the Arthropleura’s fully intact head, including antennae, stalked eyes, mandibles, and maxillae.
These findings were published in Science Advances and provide the most comprehensive view of the creature’s morphology to date.
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Analyses by paleontologist James Lamsdell reveal that Arthropleura combines characteristics typical of both millipedes and centipedes. Two pairs of legs per body segment align with modern millipedes, while its fully enclosed mandibles and distinct second maxillae resemble those of centipedes. The presence of stalked eyes—an adaptation common in aquatic crustaceans—adds another layer of uniqueness.
These discoveries lend morphological support to the molecular hypothesis that millipedes and centipedes belong to a single clade, Pectinopoda. As Lamsdell notes, “Arthropleura may be the first morphological evidence corroborating this molecular-based relationship.”
While many questions remain about the life habits and ecological role of Arthropleura, the 2024 head reconstruction marks a significant milestone in our understanding of prehistoric arthropods.
