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VERNAL — A recently discovered fossil in southeast Utah appears to show the type of prey that predators feasted on back in the age of dinosaurs and when the region wasn't quite the desert it is today.
Utah paleontologists discovered a pile of amphibian bones that they say appear to have been puked out by some sort 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 glimpse into the interactions of the animals in ancient ecosystems," said John Foster, the curator of the Utah Field House of Natural History State Park Museum and one of the study's co-authors, in a statement Tuesday.
The team discovered the fossil while scouring the Morrison Formation, a famous paleontological site known for its fossils from the late Jurassic age, which ranges from about 148 million years ago to 155 million years ago. It's mostly known for its dinosaur bones but it's also where scientists have found all sorts of other animals, such as fish, salamanders and frogs.
Southeast Utah's section of the formation mostly features prehistoric plants like ginkgoes, ferns and conifers; however, paleontologists have also found amphibians and bowfin fish there, too. These discoveries are why they believe the region was once home to either a pond or a small lake.
But during a recent survey, the team discovered an oddly 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 are among the smallest set of bones within the formation.
They added that the chemical and bone structure of the fossil indicated that it's a regurgitalite, which is a fossilized form of vomit. The team noted that it's the first finding of its kind within the Morrison Formation and also within North America's Jurassic period.
What's still not clear 150 million years later is what killed the species within the regurgitalite. Foster points out that past research puts bowfin fish in the region at the time, which he views as the "current best match" for the predator behind the fossil. Scientists have discovered fish, salamanders and frog species in the Morrison Formation for well over a century.
"Although we can't rule out other predators, a bowfin is our current suspect, so to speak," he said, explaining that fish — and other animals — do sometimes regurgitate their recent meals when they are pursued or want to distract a potential predator.
"There were three animals that we still have around today, interacting in ways also known today among those animals — prey eaten by predators and predators perhaps chased by other predators," he added. "That itself shows how similar some ancient ecosystems were to places on Earth today."
The finding is the team's most recent in the region. Two of the study's three co-authors also help discover a massive 151 million-year-old water bug, which led to a paper that was published in 2020.
James Kirkland, the state paleontologist, who co-authored both of the studies, said that paleontologists plan to continue to search 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 site in search of more tiny wonders in among the foliage."