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The word fossil can only refer to the bones of an animal—a giant t rex, a small trilobite, an average-sized giant sloth. But life can be immortalized in other, more oblique ways: in the mark an organism leaves behind as it goes about its life. Some trace fossils are almost poetic. Footprints left by a dinosaur or a burrow carved by an ancient worm begs the question: Who left it behind? Other trace fossils are less poetic but even more mysterious. The round-shaped shatter or small lump of bones raises not one but two questions: who left it and from which end? In other words: poop or snow?

All fossils require some understanding, but anything excreted or regenerated by an animal millions of years ago can be a real puzzle. The former, called coprolites, are much more common, and they often look exactly like you might expect: nubby brown lumps. But just as modern sewage is a multi-grand commodity, ancient excreta can take many forms. Some scaly brown fossils that may appear to be plain feces are actually deceivers, also known as pseudocoprolites, (The Wilkes Formation in southwestern Washington is a cluster of such elusive poop, inorganic formed When silt and soil fill the hollow pieces of wood.)

Even rarer than coprolites are regurgitlites, or fossil vomits. It is rare in the fossil record to find direct evidence of who is eating who, or who is vomiting,” said Brian Ang, a paleoartist and filmmaker. According to John Foster, curator of the Utah Field House of Natural History State Park Museum, although the soft, vegetative ice of an ancient herbivore would be less likely to have geological immortality, a hunter’s yaking may contain at least some bones. ,

Foster and his colleagues describe a new fossil regurgitalite in a paper recently published in the journal Palaios, The newly described regurgitalite is small – almost as long as a staple – but contains the scattered remains of at least two frogs and a fragment of a salamander.

When Foster’s team first excavated the rock, they thought little about it. They were working in Utah’s famous Morrison Formation, a Late Jurassic site containing a multitude of dinosaur bones including sauropods. diplodocus, whose crucified ice probably will not survive the ravages of time. But Foster and his colleagues focused on a lesser-known entourage, Morrison’s, whose abundance of fossil plants gave it its “nickname”.salad bar“There’s still a lot to be found in this formation, and some of it is going to be ice,” Ang said.

fossilized vomit containing at least two frogs and part of a salamander, resembling a pile of small bones on a tan rockCredit: Utah Field House of Natural History State Park Museum
RegurgitLite sample.

The researchers brought the specimen back to the museum, where it sat for a year amid an assortment of mysteries—”things we just can’t tell what they are,” Foster said. Some of these mysteries require two or three turns under a microscope until their identity becomes clear. For example, one of the secrets of the salad bar turned out to be a fossil water bugWhose venous fins initially appeared to be the veins of a leaf.

With a microscope, Foster realized that what he was seeing was not a plant, but a jumble of amphibian bones, some of which were just three millimeters long. And the bones didn’t come from just one, sadly separated amphibian, but a loose pile of different amphibians. The frogs were small—more than an inch or two long. “We knew we had at least two frogs,” Foster said. “We found at least one salamander bone.”

But then came the real question of sampling. “To find out,” Foster paused, “was the thing vomited up or basically passed out.”

There were some visual cues. “Most coprolites you find are basically small ovals or little tubes or something like that,” Foster said. “They maintain a kind of three-dimensional character.” But the burr of bones was flat, without a ground mass of coprolites, and the stone around it contained many fragments—the formations of sediment that probably accumulated each year around the smaller pile. But to be sure, the researchers had to do a geochemical analysis. X-ray fluorescence scans of the sample showed that the sample did not contain elevated levels of phosphorus, which would normally indicate a coprolite. The only elevated phosphorus was found in the bones, indicating that the phosphorus was not removed from the fossil in the process of turning it into rock.

The sample contained many pores of a mysterious gray mass, which also did not contain phosphorus. Foster hopes to scan the fossil at the University of Utah with a more precise machine, which will allow him to zero in on specific areas. “It would be able to give us a pretty good indication of what that unknown material is,” Foster said.

But if the fossil was vomiting, who vomited? For now, the identity of the perpetrator is lost over time. The researchers’ best guess is a fish, probably similar to a modern bowhead, due to the scales they found around the site. Other predators, such as turtles and parasitic mammals, are also a possibility, but they have yet to be discovered near the site, Foster said. Nothing bothers to bite into large, lime-sized frogs quite like a prehistoric crocodile. “The snow gives us a window into what else was going on in the ecosystem,” Ang said.

Engh, the paleoartist tasked with depicting what Regurgitlite would have looked like in real life, faced a challenge. At first, he said, he only planned to depict a fish barfing. “But then all the questions will be about why is this fish snowing? And it wouldn’t even show what the fish was eating.” To answer that question, Engh drew another sketch of a fish bitten by an alligator and tried to defy barfing—a way of distracting the predator. But without evidence of alligators in this corner of Morrison, that version was scrapped as well.

was inspired by the last illustration jaw Poster: A bowfin fish near the bottom oblivious frog, ready to bite. “I realized I still wanted the Blizzard to appear, so I added another ballfin barfing in the background,” Eng said. When the wife of Ang, an evolutionary biologist who studies the fish, noted that the lungfish would chew whatever it was eating by encapsulating it in a glob of mucus and dissolving it all, Ang found a lump of mucus in her regurgitated frog. Added sticky coating.

Illustration of a prehistoric fish approaching an unknown frog on the surface of the water, and another fish resurrecting a frog in the backgroundCredit: Brian Engu
ing is full, jaw-Inspired Scene: Two Fishes and Two Doom Frogs.

The bones inside the Regurgitlite were not super fragmented, indicating that they may have only been partially digested by the predator. Foster said it’s possible the predator may have stopped swallowing frogs defensively or after digesting the frog’s flesh in an effort to purge the frog’s bones. A mucus blob helps to hold and protect the bones together, perhaps separating the bones from scavengers or microbes, he said.

Foster is amazed that the delicate pile of small, mostly hollow bones was preserved. But his favorite part of the fossil is how it captures the interactions of modern-looking animals that lived 150 million years ago. “It kind of helps that not everything was really weird and wacky at the time of the dinosaurs,” Foster said. “Some of it will be very familiar to us.” If we were sitting on the shores of this Jurassic pond, we might have heard a chorus of frogs, Foster said, and maybe even the distinctive, timeless voice of a carnivore lifting a frog that would no longer perform the chorus.

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