This news article is based on the open-access journal article (Rebillard et al., 2026) published in Scientific Reports. The study and its figures are published under a Creative Commons Attribution 4.0 license, unless a figure contains a separate credit notice.

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Introduction: A Meal Preserved for Nearly 383 Million Years

Sometimes the best way to learn what an extinct animal ate is to study what came out the other end. That is what paleontologists did with seven unusually well-preserved pieces of Devonian fossil poop from the Sula River site in North Timan, northeastern Europe.

The scientific term for fossilized feces is coprolite. Coprolites can preserve pieces of an actual meal, including bones, scales, teeth, and spines. That gives paleontologists direct evidence of predator-prey interactions that happened hundreds of millions of years ago.

In a study published August 10, 2026 in Scientific Reports, Arnaud Rebillard and colleagues used intense X-rays to digitally open the coprolites. Inside were remains of several kinds of fishes. By comparing those remains with body fossils from the site, the team reconstructed part of a food web, the network showing which organisms eat other organisms in an ecosystem.

The result is a direct look at feeding relationships in a lake ecosystem around 383 million years ago, near the boundary between the Middle and Late Devonian.

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A Short-Lived Devonian Lake Between Lava Flows

The fossils come from the Kumushka Formation in North Timan. The site lies along the Sula River, close to Sula Waterfall, where a thin layer of fine sediment is preserved between ancient basalt lava flows. The finely laminated sediments suggest that the animals lived in or around a quiet, short-lived lake in an active volcanic landscape.

This was during the Devonian Period, often called the "Age of Fishes" because jawed vertebrates diversified dramatically in the world's seas, rivers, and lakes. The Sula deposits sit near the transition from the Givetian Stage of the Middle Devonian to the Frasnian Stage of the Late Devonian, placing the ecosystem at roughly 383 million years old.

The fossil layer contains an impressive variety of fish remains. Paleontologists have found large lobe-finned fishes such as Laccognathus, Glyptolepis, and an Eusthenopteron-like fish, along with lungfishes, acanthodians, and armored placoderms. Plant fossils are present too, including the lycophyte Helenia and the progymnosperm Callixylon. A progymnosperm was an extinct woody plant related to the evolutionary line that later produced seed plants.

The reconstruction at the top of the page shows this unusual mix of lake life and nearby volcanic activity.

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How Scientists X-Rayed Fossil Poop Without Breaking It

Earlier work had revealed fish scales and possible soft-tissue traces inside the coprolites, but cutting thin sections destroys part of a specimen. For this study, the researchers used synchrotron microtomography at the European Synchrotron Radiation Facility in Grenoble, France.

A synchrotron is a large particle-accelerator facility that can produce extremely bright X-rays. Microtomography works much like a medical CT scan, but at much finer scales. Thousands of X-ray views are combined into a three-dimensional digital model, allowing researchers to look through a fossil slice by slice and then virtually separate individual objects inside it.

That meant the team could digitally "dissect" the coprolites without physically cutting them apart. Tiny skeletal fragments only a few millimeters across could be isolated, rotated, enlarged, and compared with known fish anatomy. Some were preserved well enough to identify specific types of bones, teeth, scales, and fin spines.

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What Was Inside the Devonian Coprolites?

The scans showed that these were not simple masses of digested material. The seven coprolites contained a surprisingly diverse collection of fish remains. The most common belonged to lungfishes, or dipnoans - the same broad group represented today by living lungfish. The researchers identified tooth plates, skull fragments, ribs, and parts of the shoulder girdle from small Devonian lungfish.

Acanthodian remains were also extremely common. Acanthodians were extinct spiny jawed fishes important to the early evolutionary history of jawed vertebrates. In several coprolites, their tiny scales numbered in the thousands. Fin spines and other skeletal parts were preserved as well.

The scans also revealed pieces from sarcopterygians, or lobe-finned fishes. This group includes lungfish and coelacanths, as well as the branch of vertebrate evolution from which tetrapods eventually arose. Some remains were attributed to Glyptolepis, a predatory lobe-finned fish known from body fossils at the site.

One of the most intriguing details was the size of some lungfish bones. Shoulder elements less than 5 millimeters long appear to have come from juveniles. The researchers suggest that a nursery or spawning area may have been nearby. If so, the Sula lake may have been more than a place where adult fishes hunted; it may also have been an important breeding habitat.

A thin plant fragment was found inside one coprolite as well. The predator may simply have swallowed it while taking prey or feeding near the bottom.

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A Spiral Clue to the Animal That Left It Behind

Figuring out what was eaten is easier than identifying the animal that produced a coprolite. Fossil feces are trace fossils, evidence of an organism's activity rather than part of its body, so the producer is rarely obvious.

Two of the best-preserved specimens contained prey remains arranged in an internal spiral. That pattern is important because many early fishes had a spiral valve in the intestine. Instead of a long coiled intestine like ours, the gut contained an internal spiral fold that slowed food and increased the surface area available for digestion. Similar structures still occur in some living fishes, including sharks and lungfish.

By combining the coprolites' size, shape, contents, and internal structure with the large fishes known from the site, the researchers narrowed the list of possible producers. Laccognathus, Glyptolepis, and Eusthenopteron were all considered plausible large predators. Laccognathus was the strongest candidate for two coprolites with spiral internal architecture, while Eusthenopteron was suggested for two specimens without that distinctive pattern.

These identifications remain hypotheses. Assigning a trace fossil to one exact producer is difficult, but the coprolites clearly show that large Devonian predators were eating several kinds of fishes at Sula.

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Reconstructing a 383-Million-Year-Old Food Web

This is where the fossil poop becomes especially useful. A body fossil can tell us that a fish lived at Sula. A coprolite can tell us that one kind of fish actually ate another. When the researchers combined those feeding clues across all seven coprolites, they found evidence for several trophic levels - steps in a food chain based on how organisms obtain energy.

The study places acanthodians among the primary and secondary consumers, lungfishes among secondary consumers, and Glyptolepis as a tertiary consumer. Some coprolites contain prey from three trophic levels at once, suggesting large predators ate a broad range of prey. That mix is strong evidence for a food web with several feeding relationships, rather than a simple one-predator, one-prey pattern.

No Placoderms?

There is an interesting absence too. Armored placoderm fossils occur at Sula, but the researchers did not identify placoderm remains inside the studied coprolites. Perhaps the placoderms occupied a different niche, were only temporary visitors, were not common prey for these predators, or had hard armor that was regurgitated instead of swallowed. More coprolites will be needed to test those possibilities.

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Why Fossil Poop Can Tell Us More Than a Skeleton

Although Devonian coprolites are known from many places, what makes the Sula material unique is the combination of exceptional preservation, multiple coprolites, identifiable prey remains, and high-resolution 3D imaging. Together, those ingredients let the researchers reconstruct relationships within an ecosystem rather than simply list the animals that were present.

Skeletons and teeth tell us which animals were present, but interactions are harder to preserve. Coprolites can record behavior. A scale trapped inside fossil feces shows that one animal consumed another.

At Sula, those clues point to a quiet lake with small acanthodians and juvenile lungfishes, larger predatory fishes, shoreline vegetation, and nearby volcanic activity.

Nearly 383 million years later, seven pieces of fossilized feces still preserve a surprisingly detailed record of this community. Sometimes an unglamorous fossil tells one of the best stories.

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Journal Article:

Rebillard, A., Dupret, V., Beznosov, P., & Ahlberg, P. E. (2026). Investigating a Devonian vertebrate assemblage with synchrotron microtomography of coprolites. Scientific Reports, 16, 24728. Published August 10, 2026. https://doi.org/10.1038/s41598-026-63718-2.

Image and reuse license: The article is published under the Creative Commons Attribution 4.0 International License. Figures from the article are included under that license unless a particular figure contains a separate credit line stating otherwise.

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