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A vomit with 150 million years helps us to reconstruct the prehistoric ecosystem

A team of paleontologists thought they had found a very strange new species. They had before them a mixture of bones and fossil remains difficult to rearrange. But further analysis showed that they had discovered a regurgitalite: fossilized vomit 150 million years old.

The diet of an aquatic predator

These types of findings offer an interesting opportunity to study the ecosystem that existed at that time in the area where the fossil has appeared, since it is possible to directly observe what the animal ate before vomiting . John Foster of the Utah Museum of Natural History led the study:

“This fossil gives us a rare insight into animal interactions in ancient ecosystems.”

The bromalite (fossil remains from the digestive system of organisms) could come from a fish or a semi-aquatic mammal, but it is very difficult to guess what type of animal the vomit would correspond to , impossible to know the specific species.

Among the remains that make up the fossil, a group of small bones has been detected, some of them only 3 millimeters long, attributed to animals of the lissamphibian clade (Lissamphibia). Specifically, they suggest that there are elements of a small frog or a tadpole and a salamander that, judging by the size of its bones, could be the smallest specimen reported in the entire site and its morphology resembles that of the genera Valdotriton and Iridotriton. .

It will be difficult to specify more about what the fossil contains. We have before us the diet of an animal from millions of years ago, but we do not know the diner. And it is that, if it is already an arduous and complex job to reconstruct the puzzle of a fossilized animal, the paleontologists of this discovery face pieces of several puzzles that, inevitably, will remain incomplete. But that does not stop adding rich information about the past of our planet.

The Morrison Formation

Specifically, it is about new information about the ecosystem of the southeast of the current state of Utah during the Upper Jurassic, about 150 million years ago . In this period dominated by the dinosaurs, this region of North America would not be as desert as it is today, but rather had ponds or lakes in which fish or semi-aquatic mammals could have lived, to which the fossilized vomit is attributed.

The team of paleontologists included members of the Utah Geological Survey, the Utah Museum of Natural History and the Flying Heritage and Combat Armor Museum in Washington. They found the fossil during an expedition through the Morrison Formation, an Upper Jurassic geological formation famous for discoveries of dinosaur fossils found in its rocks. With remains spanning from about 155 to 148 million years ago, the Morrison Formation spans the western United States and part of Canada. The first remains located in the formation were discovered in 1877 and to date new fossils have not stopped appearing, including those of Diplodocus , Stegosaurus and Allosaurus , as well as the remains of other vertebrates such as crocodiles and fish. During the Jurassic, this area was watered by seasonal rivers and lakes whose sedimentary deposits became a luxury preserver for the fossils we find today.

Scientists will continue to search for more clues that may bring us closer to the predator that enjoyed (for a short time) fossilized food, as well as new discoveries that will shed light on the paleoecosystem of the North American West during the Jurassic.


Foster, J. et al. 2022. Significance of a small regugitalite containing lissamphibian bones, from the Morrison Formation (Upper Jurassic), qithin a diverse plant locality deposit in southeastern Utah, USA. Palaios 37, 8, 433-442. DOI: 10.2110/palo.2021.058.

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