What Scientists Learned From a Trove of Fossilized Archosaur Poop and Vomit

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Dinosaur coprolites are rare treats that offer paleontologists prized glimpses into the long-lost lifestyles of "terrible lizards." Coprolites were once feces, which do not fossilize as readily as hard, durable bones. Yet they tell stories that bones do not, like what dinosaurs ate, what their digestive tracts were like, and how big their anuses were (a clue to overall size).

Biologists from Sweden's Uppsala University were lucky enough to uncover a treasure trove of coprolites, and even a few fossilized "regurgitates" (vomit), in a clay pit outside of Lisowice, Poland. They recently published their analysis of the finds in the journal Scientific Reports.


Judging from footprints and bone fossils found nearby, it seems the coprolites belonged to S. wawelski, more commonly known as Smok, meaning "dragon" in Polish. Alive roughly 200 million years ago, Smok was a 16 to 20-foot-long carnivorous archosaur that shared features with both crocodiles and dinosaurs. It may have been one of the earliest forerunners of the infamous Tyrannosaurus rex.

Like T. rex, Smok may also have been a bone cruncher, according to the new results. Doctoral student Martin Qvarnström and his colleagues examined the coprolites uncovered at the clay pit with synchrotron microtomography, a form of 3D imaging that utilizes electromagnetic radiation from a particle accelerator. This allowed them to effectively see inside the feces, revealing that they were filled with bone fragments and broken teeth. The fragments were difficult to match to specific prey species, but some likely belonged to an early amphibian and a juvenile dicynodont.

Close to the coprolites, the researchers also found fossilized vomit containing larger bones.

"This suggests that S. wawelski regurgitated larger, indigestible, fragments in a manner comparable to modern birds such as owls," they wrote.

As powerful as some predatory dinosaurs were, bone-chewing and eating was fairly uncommon, as it required massive skulls, strong jaws, and robust teeth to withstand the crunching forces involved. Teasing the grinding nature of this behavior, the researchers found a few of Smok's own teeth in its feces, suggesting that it broke and involuntarily swallowed them as it consumed its prey.

Qvarnström and his colleagues compared Smok's bone-biting eating style to that of a hyena, which is also similar to the tyrannosaurids of the Late Cretaceous, but strangely unlike modern archosaurs – birds and crocodilians – which consume prey with little chewing and can fully digest bones.

Source: Martin Qvarnström, Per E. Ahlberg & Grzegorz Niedźwiedzki. Tyrannosaurid-like osteophagy by a Triassic archosaur. Scientific Reports volume 9, Article number: 925 (2019) https://doi.org/10.1038/s41598-018-37540-4

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