Hundreds of millions of years ago, a carnivorous creature ate a feast of prehistoric amphibians — and then vomited up its meal.
Now paleontologists have unearthed the burp and published their findings on the ancient upchuck.
In 2018, researchers discovered regurgitalite — fossilized remains of an animal’s stomach contents, also known as bromalite — during an excavation in the southeastern Utah portion of the Morrison Formation.
Stretching across the western United States, this strip of sedimentary rock is a breeding ground for Late Jurassic fossils (164 to 145 million years ago).
This section in particular, dubbed the “Jurassic Salad Bar” by local paleontologists, contains the fossilized remains of plants and other organic matter rather than animal bones.
When a team that included researchers from the Utah Geological Survey (UGS) stumbled upon the “compact little pile” of regurgitated remains measuring no more than a third of an inch square, they knew they had found something Special, the scientists reported in a study published on 12 25 in the diary Palaios.
“What struck us was this low concentration of animal bones in a relatively small space,” lead author John Foster, curator of the Utah Field House of Natural History State Park Museum in Vernal, told Live Science.
“There are usually no animal remains at this site, only plants, and the bones we found were not laid out [amongst the rock] but concentrate on this one spot. These are the first bones we’ve ever seen there.”
Initially, the team was unaware that they had found prehistoric vomit. Instead, the scientists thought they had discovered the bones of a living thing, until they “realized that some of them looked fake and not all came from a single salamander,” Foster said.
“On closer inspection, most of the material comes from a frog and at least one salamander. It was then that we began to suspect that what we were seeing was being vomited up by a predator.”
These remains include amphibian bones, particularly thigh bones from a frog and a salamander, as well as vertebrae from one or more unidentified species.
In all, nearly a dozen bone fragments were found along with a matrix of fossilized soft tissue, according to the study.
And unlike coprolites (fossilized feces), this burp isn’t fully digested, leading researchers to conclude it’s a burp.
Although there are a number of regurgitalite finds around the world, Foster said this is the first known case of regurgitalite in the Morrison Formation, calling the discovery “unique”.
While there’s no way to know exactly which animal species lost its lunch millions of years ago — or why it choked in the first place — further analysis could determine other components of the partially digested animals the predator swallowed.
“We think there’s more to this thing than just the tiny amphibian bones,” Foster said. “By doing a chemical analysis, we can start to rule things out and determine what exactly the soft tissues are made of.”