Paleontologists Find 150-Million-Year-Old Jurassic Barf in Utah

You’ve heard of Jurassic Park, but what about Jurassic barf? Paleontologists in Utah believe that they have found exactly that—a fossilized pile of vomit—which dates back an astonishing 150 million years, revealing an extremely rare glimpse of a meaty Jurassic meal that just wouldn’t stay down.

The dinosaur-age retch contains assorted amphibian bones, including a frog and a very small salamander, that were swallowed by a small predator, probably a fish or semi-aquatic mammal, according to a recent study published in the journal Palaios. 

Researchers led by John Foster, a paleontologist and curator at the Utah Field House of Natural History State Park Museum, discovered the regurgitated remains in 2018 within the Utah patch of the Morrison Formation, a vast Jurassic fossil bed that extends across much of North America. The specimen, which contains parts of a frog and a salamander, was found at a site called the “Jurassic salad bar” because it is so dominated by fossilized plants, and is the first “regurgitalite” ever found from the Jurassic era in all of North America.

“We didn't immediately recognize it for what it was, and in fact, we didn't even realize it was bone until much later, back at the museum, when we looked at it under a microscope and saw that it was tiny bones and not a badly preserved plant fossil,” Foster said in an email. “When we realized that the pile of bones appeared to represent at least three individuals and likely two different types of amphibians we really started to think that something was up and this wasn't just a ‘typical’ few bones of small vertebrates. Somehow these bones had gotten concentrated.”

“With no mechanical process we could identify in a small, quiet lake setting, we started looking for biological causes, and that's when we began to suspect that the pile of bones had come out of a predator,” he continued. “Then we needed to determine, essentially, which end it came out of.”

To that point, this preserved puke is part of a wider class of fossils from digestive systems, known as bromalites, which also includes fossilized poops, called coprolites. Bromalites not only provide a visceral look at the diets of extinct species, they can also provide insights into the wider ecosystems inhabited by predator and prey—or alternately, barfer and barfee. Though fossilized bones and tracks can tell scientists a lot about extinct animals that lived millions of years ago, bromalites can open an exceptional window into the bellies of ancient creatures.

“Bromalites can show direct evidence of who was feeding on what,” Foster explained. “Stomach contents for example show what the animal was eating. Coprolites can show the same thing, although because they are not found within a skeleton like stomach contents are, it is harder to know what made them. Regurgitalites similarly can show us what a predator was eating but determining for sure who that predator was can be a bit difficult.”

“Bromalites include stomach contents (usually found within another fossil), coprolites that have made it all the way through the digestive system, and regurgitalites that of course come back out the mouth,” he continued. “There are also cases of skeletons with intestinal contents preserved in place. In regurgitalites the fossil material tends to be less fully digested that coprolites.” 

The researchers weighed all these factors as they tried to figure out whether their rare specimen was barfed or pooped. The team conducted geochemical analyses on the specimen that “suggested it had been more likely puked,” because the bones lacked the elevated levels of phosphorus normally seen in coprolites, Foster said. 

Foster and his colleagues think these small amphibians were likely devoured by something like a bowfin fish within the rich aquatic landscape that once blanketed this portion of Utah. Some modern fish will throw up their food when pursued by a predator, so it’s possible that this Jurassic swimmer lost its lunch while trying to avoid becoming something else’s lunch.

“We plan to try to further identify the non-bone, non-matrix material in the fossil with another instrument, hopefully this winter,” Foster said. “If we are lucky, we will be able to determine if this material is soft tissue, which would help confirm that it is a regurgitalite.”

“We have also been working the site some more (as recently as last week) and continue to find bowfin fish elements but no other possible predators yet,” he added.

To that end, Foster’s team plans to keep studying this fossilized barf bag for more clues about the unfortunate amphibians within it, and the predator that spewed it into the fossil record 150 million years ago

“We've known for a while that the Morrison Formation had frogs and salamanders (and bowfin fish as possible predators), but this fossil shows the first direct evidence of amphibians as prey animals in a Late Jurassic pond or lake in North America,” Foster said. 

“The fact that we can't be certain of the predator is a little disappointing,” he noted, however the fact “that we can see amphibians being eaten by a predator and that predator, for whatever reason, regurgitating the meal gives us a small window into Late Jurassic pond life that wasn't all that different from what we might see in a similar setting today.”

Update: This article has been updated to include comments from study lead John Foster.