Initially published in 1865, Palaeocampa anthrax predated the discovery of the Burgess Shale in Canada by nearly 50 years. Over the next 130 years, it underwent various classifications until Richard Knecht and his team at the University of Michigan identified its true nature. This organism primarily inhabited freshwater environments, challenging the notion that Paleozoic Robopodians were exclusively marine.
Reconstruction of the Moncole-Le Mines-Lagertet Environment Palaeocampa anthrax: The large Palaeocampa anthrax is illustrated on the banks of a shallow inland river, concealed by dense vegetation and coal forest mist, alongside various euticulcinoids and a pair of freshwater Xiphosrans, Alanops magnificus; the nearest marine environment is several hundred km southwest. Image credit: Knecht et al., doi: 10.1038/s42003-025-08483-0.
Robopodians are extinct, soft-bodied organisms that connect primitive worm-like ancestors to modern arthropods such as insects and crustaceans.
Their iconic fossils are mainly associated with Cambrian marine sediments like Burgess Shale, including Hallucigenia and Aysheaia pedunculata, the latter discovered in 1911, long thought to be exclusively marine.
“Robopodians may have been prevalent on the Paleozoic seabed, but aside from microscopic creatures and terrestrial velvet worms, we believed they were confined to the ocean,” stated Dr. Knecht.
In their recent study, Dr. Knecht and his co-authors examined 43 specimens of Palaeocampa anthrax, utilizing advanced imaging techniques from two Carboniferous Lagerstätten (Mazon Creek, USA, and Moncole Mines, France), including backscattering scanning electron microscopy (SEM) and energy dispersive spectroscopy.
The analysis revealed intricate anatomical traits, with nearly 1,000 hairy spines covering its body being particularly noteworthy.
Chemical residues at the spine tips were identified using Fourier transform infrared spectroscopy (FTIR), indicating potential secretion of toxins to deter predators in wetland habitats.
“I was surprised to find that fragments of biological molecules can be exceptionally well-preserved or altered in fossilized geological materials,” remarked Nanphungyu, a paleontologist at Columbia University.
“We’re thrilled about this technology’s ability to distinguishing fossilized remains from rocky matrices.”
Palaeocampa anthrax from Mazon Creek Lagerstätte. Image credits: Knecht et al., doi: 10.1038/s42003-025-08483-0.” width=”580″ height=”701″ srcset=”https://cdn.sci.news/images/2025/07/image_14089_2-Palaeocampa-anthrax.jpg 580w, https://cdn.sci.news/images/2025/07/image_14089_2-Palaeocampa-anthrax-248×300.jpg 248w” sizes=”(max-width: 580px) 100vw, 580px”/>Palaeocampa anthrax from Mazon Creek Lagerstätte. Image credit: Knecht et al., doi: 10.1038/s42003-025-08483-0.
The research team posits that Palaeocampa anthrax is closely related to the Hadranax Cambrian Robopodian from Greenland, which is nearly 200 million years older.
Both species are blind, possess 10 pairs of legs, and lack claws. However, Hadranax adapted to navigate deep waters with elongated front appendages, while Palaeocampa anthrax, measuring only 4 cm, had a dense covering of spines over its legs, suggesting it might have thrived in freshwater, perhaps even amphibious environments.
This finding also clarifies the enigma surrounding the Moncole-le-Mines fossil site, which was once thought to be marine.
“Mazon Creek is characterized by a mixture of terrestrial, freshwater, and marine fauna,” Dr. Knecht elaborated.
“In contrast, Moncole-le-Mines, which yielded half of the specimens, was located hundreds of kilometers inland, thus ruling out any marine origin.”
“This reclassification confirms the site’s non-marine nature, offering a unique insight into ancient freshwater ecosystems.”
This discovery broadens our comprehension of Robopodia diversity and poses new evolutionary questions. How many more species could migrate from ocean to freshwater, hidden away in museum collections and misidentified?
“The rarity of conditions conducive to fossilizing soft-bodied creatures such as Robopodians makes this finding significant,” Dr. Knecht concluded.
“While most insights come from Cambrian Lagerstätten, such as Palaeocampa anthrax, opportunities from the Carboniferous Period are scarce, making each new discovery incredibly valuable.”
The results will be published in the journal Communication Biology.
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RJ Knecht et al. 2025. Palaeocampa anthrax: armored freshwater robopod with chemical defenses from the Carboniferous. Commun Biol 8, 1080; doi:10.1038/s42003-025-08483-0
Source: www.sci.news
