About 66 million years ago, just before the mass extinction that wiped out the dinosaurs, a fish chewed up and spit out some sea creatures. Unbeknownst to that fish, its rejected meal was preserved in fossil form.
And it's now arrived at a museum in Denmark.
The fossil was found at Stevns Klint, a cliff in eastern Denmark known for its fossil record and important geologic history. Fossil hunter Peter Bennicke discovered it in a piece of chalk at the UNESCO World Heritage site and brought it to Denmark's East Zealand Museum.
"It is truly an unusual find," Jesper Milàn, a curator at one of the museum's exhibits, said in a press release. "Such a find provides important new knowledge about the relationship between predators and prey and the food chains in the Cretaceous sea."
Why this meal was spat out
There's a fancy word for fossilized vomit: regurgitalite.
Paul Olsen, a professor of earth and environmental sciences at Columbia University who was not involved in the fossil find, said regurgitalites are not rare, but this one is an "especially nice example."
"This particular fossil, if you look carefully at the image that's provided, you see that the edges of the fossils are very sharp and clear. And that tells you that this material did not pass into the digestive system of whatever was doing the chewing," he says. (And to be technical, it's not vomit, because that means food reaches the stomach. He calls it a "gastric ejection" instead, likening it to chewing on and spitting out sunflower seed shells.)
The predator was attempting to eat sea lilies, also called crinoids. The deep-sea creatures, which could be mistaken for plants, still exist today.
The fossil also appears to contain bryozoans, Olsen says, very tiny creatures that are also called moss animals, but it's unclear if they were part of the fish's attempted meal in this case. Both crinoids and moss animals would be common in that area at the bottom of the sea at the time.
Unfortunately for this fish, crinoids don't have much nutrition and have a coating of mucus that can be toxic to fish.
"It could be that whatever made this regurgitalite was cruising about looking for fish, maybe fairly desperate for food, and picking up crinoids and whatever else it could in its mouth, chewing it up. And this particular mouthful may have been really foul. And that's why there are still bits of unchewed crinoid in it," he says.
There were thousands of species of fish in the area at the time, so it's not clear what type of fish did the chewing.
Vomit is one of several types of "trace fossils"
Regurgitalites are one type of "bromalite" — fossilized digestive material. There are also colonites, where the food was found inside the intestines, and coprolites — fossilized poop.
Bromalites are in turn part of the record of "trace fossils." They aren't the remains of the animal itself, but of how it lived.
"Regurgitalites give us a window into the feeding processes of various members of the ecosystem that were around at the time," Olsen says.
These types of fossils are "a wonderful illustration of things that were going on just before the giant [asteroid] impact, normal life in the ecosystem. It's a trace of that action. ... It's a trace of the organisms doing their business on a daily basis."
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