Marrakech – A team of Moroccan researchers has identified a new species of trace fossil left by trilobites roughly 360 million years ago in the eastern Anti-Atlas mountains. The study was published online Wednesday in Acta Palaeontologica Polonica, a peer-reviewed paleontology journal.
The research was led by Wahiba Bel Haouz, Mehdi Maanan, and Lahssen Baidder of Hassan II University in Casablanca, alongside Abdelouahed Lagnaoui of Hassan First University in Berrechid. Christian Klug of the University of Zürich co-authored the study.
The team analyzed more than 60 specimens collected between 2018 and 2025 from the Aoufilal Formation near the villages of El Khraouia and Taouz, on the Tafilalt Platform. The fossils date to the Famennian stage of the late Devonian period, approximately 372 to 359 million years ago. That places them just before one of Earth’s major mass extinctions, the Hangenberg Event.
Trace fossils are not body remains of ancient organisms. They are marks left behind by animal activity, such as crawling trails, resting impressions, and burrows. The assemblage described in the study is dominated by trilobite traces but also includes marks left by worms, crustaceans, bivalves, and fish.
The team’s central finding is the introduction of Rusophycus antiatlasensis, a new trace fossil species named after the Anti-Atlas region. It consists of short, bilobate impressions with an oblong to ovate outline and a distinctive cylindrical median furrow.
The authors suggest this furrow could be an imprint of the trilobite’s digestive tract. Up to eleven of these traces appear in serial arrangement on a single slab, which the researchers interpret as evidence of gregarious behavior among the trilobites that made them.
The study also reports the youngest known occurrence of Cruziana lobosa, a well-known trace fossil first described in 1970. Previously, its most recent record came from the Middle Devonian of Libya. The Moroccan specimens extend its range into the latest Devonian.
A shallow sea alive just before mass extinction
One of the study’s more striking conclusions concerns trilobite behavior. Several slabs show Diplichnites walking trackways that transition directly into Rusophycus resting traces, made by the same animal. The authors interpret this as possible predatory stalking.
“The producer being on the lookout and stalking for its prey; it took a resting position so that its prey does not sense its presence,” the paper states. Alternatively, the trilobites may have been hiding from predators. Fish swim traces, classified as Undichna, appear on the same bedding surfaces.
The full assemblage includes twelve identified trace types representing five categories of animal behavior: grazing, locomotion, resting, feeding, and dwelling. The researchers assign the assemblage to the Cruziana ichnofacies, which indicates a shallow-marine environment with low wave energy, stable substrates, and regular organic matter supply.
The findings paint a detailed picture of what the waters off eastern Morocco looked like during the final stretch of the Devonian. The area sat on the passive continental margin of northwestern Gondwana at a moderate southern latitude. Waters were shallow, likely well under 500 meters deep, and at times reached the photic zone where sunlight penetrates.
Salinity was normal. Bottom conditions alternated between well-oxygenated phases and repeated episodes of low oxygen. The sea supported a diverse ecosystem of trilobites, cephalopods, bivalves, brachiopods, crinoids, and fishes.
“Judging from the diversity of the invertebrate and vertebrate trace fossils and previously described fish and cephalopod remains, a shallow marine ecosystem was present during the latest Devonian in the eastern Anti-Atlas,” the authors wrote.
By the late Devonian, trilobite diversity had already declined sharply from earlier periods. Only two orders survived into the Famennian: Phacopida and Proetida. Based on size measurements, the authors suggest phacopid trilobites were the most likely producers of the Cruziana lobosa traces, while both phacopids and proetids may have made the Rusophycus and Diplichnites tracks.
The specimens are housed at the Life Traces Museum of the Higher School of Education and Training of Berrechid. The authors call for more intensive fossil exploration in the eastern Anti-Atlas, given the region’s importance for understanding how marine ecosystems evolved through the late Devonian extinction events.
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