Hundreds of millions of years ago, a carnivorous creature devoured a prehistoric amphibian’s feast—and vomited its meal afterward.
Now, paleontologists have discovered regurgitation and published their findings on ancient reflux.
In 2018, researchers discovered the fossilized remains of an animal’s stomach contents, also known as bromelite, while excavating in the southeastern part of Utah from the Morrison Formation.
This patch of sedimentary rock that stretches across the western United States is a hotbed of fossils dating back to the late Jurassic (164 million to 145 million years ago).
This section in particular, which local paleontologists have dubbed the “Jurassic salad bar,” usually contains fossilized remains of plants and other organic matter, rather than animal bones.
So, when a team including researchers from the Utah Geological Survey (UGS) found a “small, compacted pile” of crumbled remains measuring no more than a third of a square inch (1 square centimeter), they knew they had found something special, he reported. Scientists in a study published August 25 in the journal Palios.
“What surprised us was this small concentration of animal bones in a relatively small area,” lead author John Foster, curator of the Utah Field House Museum of Natural History in Vernal, told Live Science.
“Normally there are no animal remains at this site, only plants, and the bones we found were not scattered [amongst the rock] But they focused on this one spot. These are the first bones we’ve ever seen there.”
At first, the team didn’t know they had found prehistoric vomit. Instead, scientists thought they had discovered the bones of a single creature, until “they realized that some of them looked wrong and they weren’t all from a single salamander,” Foster said.
“If we look closely, most of the material is from at least one frog and salamander. That’s when we started to suspect that what we were seeing was being subdued by a predator.”
Those remains include the bones of amphibians, specifically the femurs of A frog and salamanders, as well as vertebrae of one or more unknown species.
Finally, nearly a dozen bone fragments were found clustered together, along with a matrix of ossified soft tissue, according to the study.
And unlike coprolites (fossilized tube), this regurgitation is not completely digested, leading researchers to determine that it is regurgitation.
Although there have been a number of recorded discoveries of omentums around the world, Foster said this is the first known example of one in a Morrison formation, describing the find as “unique.”
Although there’s no way to know exactly what kind of animal lost its diet millions of years ago – or why it became so common in the first place – further analysis can identify other components of partially digested animals ingested by the predator.
“We think this thing is more than just the bones of a small amphibian,” Foster said. “By doing a chemical analysis, we can begin to rule things out and identify the exact components of the soft tissue.”