Fossilized vomit reveals 290-million-year-old predator’s diet

Two hundred and ninety million years ago, in a mountain valley within the central region of the supercontinent Pangaea, an apex predator snapped up at least three other animals and sometime later puked up the bones.

That material hardened over the ages, and is now the oldest fossilized vomit ever discovered from a land-based ecosystem. The cluster of bones and digestive material provides rare information, published January 30 in Scientific Reports, about the behavior of some of the world’s earliest land predators.

“It’s kind of like a photograph of a moment in the past that is telling us about the animal that was living,” says Arnaud Rebillard, a paleontologist at Museum für Naturkunde in Berlin. “Any data that we can find about their behavior is very precious.”

Paleontologists discovered the lime-sized specimen in 2021 at a site called the Bromacker locality in central Germany. Researchers then scanned the bones to create 3-D models showing a cluster of parts from different animals, suggesting they had come from a predator’s gut. They also chemically analyzed the material surrounding the bones and found that it was low in phosphorus, suggesting it was not a fossilized dropping.

While the specific predator that regurgitated the bones is unknown, the researchers strongly suspect that it was one of two animals that resemble today’s monitor lizards like Komodo dragons: Dimetrodon teutonis, with a prominent sail on its back, and Tambacarnifex unguifalcatus. Though reptilian in appearance, both are from a group of animals called synapsids that includes mammals and their extinct relatives.

Among the 41 disgorged bones, the researchers were able to distinguish two small lizardlike reptiles and a limb bone from a larger reptilelike herbivore. This collection of remains, along with several unidentified bones, indicates that the predator ate whatever it could find rather than specializing in a specific type of prey.

Because the fossilized vomit, or regurgitalite, contains three different animals eaten by one predator, “we can literally say, for sure, that these three animals were living at exactly the same place and exactly the same time, maybe to the week or even to the day,” Rebillard says.

Several living predators habitually regurgitate bones and other body parts that are tough to digest after eating. Scientists don’t know if this is why the ancient animal spit up the bones, but it is one of the most plausible explanations, along with simply overeating, Rebillard says.

Fossils of partially digested material, including regurgitalites, as well as fossilized feces, are valuable clues for studying Earth’s past. “We need fossils like this to really tie together how the ecosystem functioned and how the food webs were structured,” says Martin Qvarnström, a paleontologist at Uppsala University in Sweden who was a reviewer on the paper.

The German regurgitalite is particularly exciting because the Bromacker site preserves a snapshot of an early terrestrial ecosystem. Older predators that could travel on land often lived in semiaquatic environments where they hunted crustaceans and fish. The Permian period represents a time when large herbivores became prominent in inland environments, followed by new predators. Fossil dung and vomit are much rarer in inland environs than in aquatic ones.

“We’re talking about almost 300-million-year-old ecosystems,” Rebillard says. “So to have such a temporal vision about this to the day they were living, in the same area and the same moment, is extremely fascinating.”