150-million-year-old vomit found in Utah provides ‘rare insight’ into prehistoric ecosystems

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VERNAL — A newly discovered fossil in southeastern Utah appears to show the type of prey predators feasted on back in the age of dinosaurs, when the region wasn’t quite the desert it is today.

Utah paleontologists discovered a pile of amphibian bones that they say appears to have been thrown out by some kind of predator. This prehistoric vomit is believed to be 150 million years old, according to paleontologists with the Utah Geological Survey, Utah Division of State Parks and the Flying Heritage & Combat Armor Museum in Washington.

Their findings were published in the journal Palaios last month.

“This fossil gives us a rare insight into animal interactions in ancient ecosystems,” John Foster, curator of the Utah Field House of Natural History State Park Museum and one of the study’s co-authors, said in a statement Tuesday.

The team discovered the fossil while scouring the Morrison Formation, a famous paleontological site known for its Late Jurassic fossils, which span from about 148 million years ago to 155 million years ago. It’s best known for its dinosaur bones, but it’s also where scientists have found all sorts of other animals, such as fish, salamanders and frogs.

The southeastern Utah section of the formation has mostly prehistoric plants such as ginkgos, ferns, and conifers; however, paleontologists have also found amphibians and bowfin fish there as well. These discoveries are why they believe the region was once home to either a pond or a small lake.

But during a recent study, the team discovered a strangely arranged fossil. It was a cluster of bones that included “elements” of at least one small frog or tadpole and would be the “smallest reported salamander specimen from the formation,” the researchers wrote in the study. Some of these bones were only 0.12 inches long, which is among the smallest sets of bones in the formation.

They added that the chemical and bone structure of the fossil indicated that it is a regurgitalite, which is a fossilized form of vomit. The team noted that it is the first find of its kind in the Morrison Formation and also within the Jurassic period of North America.

What is still not clear 150 million years later is what killed the species in the regurgitate. Foster points out that previous research puts bowfin fish in the region at the time, which he considers the “current best match” for the predator behind the fossil. Scientists have discovered fish, salamanders and frog species in the Morrison Formation for more than a century.

“While we can’t rule out other predators, a bowfin is our current suspect, so to speak,” he said, explaining that fish — and other animals — sometimes abandon their latest meals when they’re being chased or want to distract a potential predator.

“There were three animals that we still have around today that interact in ways that are also known among these animals today — prey eaten by predators and predators perhaps hunted by other predators,” he added. “That in itself shows how similar some ancient ecosystems were in places on Earth today.”

The find is the team’s latest in the region. Two of the study’s three co-authors also help discover a massive 151-million-year-old water fault, which led to a paper published in 2020.

James Kirkland, the state paleontologist who co-authored both studies, said paleontologists plan to continue searching the site where the prehistoric vomit was discovered to see if they can find more evidence of the region’s past ecosystem.

“I was so excited to have found this site, as Upper Jurassic plant localities are so rare,” he said in a statement. “We must now carefully dissect the place in search of more little wonders in the foliage.”

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