A 75-million-year-old fossil is the first dinosaur to be found with stomach contents

A tyrannosaur’s last meal was first discovered in a fossil showing a juvenile Gorgosaurus With his stomach contents in place. This type of dinosaur only ate the legs of two small feathered dinosaurs, which were likely a common and abundant menu item about 75 million years ago. Setipes elegans It is now better known from fossilized stomach contents.

“It is somewhat unfortunate for the residents of Setipes, but fortunate for us,” said study co-author Dr. Darla Zelenitsky from the University of Calgary IFLScience said. Zelenitsky describes Gorgosaurus As a “one-time fossil of her career” – although it is worth noting that her career has included only a few such fossils to date – because of its uniqueness as the first tyrannosaur ever found with preserved stomach contents.

Bone deterioration tells us that Gorgosaurus He must have died within a week of ingesting it Setips His legs, but what killed him? “It is quite clear why the little one died Setips He,” jokes the co-author Dr. François Therrien of the Royal Tyrrell Museum. “But as for the cause of death Gorgosaurus? We have no idea, however [it] “Maybe he didn’t die of indigestion.”

“The dinosaur’s body was found at the bottom of the sediment of the river channel, but this does not necessarily mean that it drowned in the river. It is an ideal environment for burial, because rivers transport a lot of sediment.”

François Therrien (right) and Darla Zelenitsky (left) with Gorgosaurus Fossil with preserved stomach contents.

Image source: Royal Tyrrell Museum of Paleontology

The moment of death can have a major impact on our ability to recognize extinct animals, especially when it comes to their behavior that is rarely recorded in fossils. Exceptions to this have been found in the Gobi Desert in Mongolia, where ancient animals sometimes died due to sudden dune collapses.

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“Say there was a rainstorm, and the sand dune collapsed on top of the dinosaurs, you would probably get [preserved] “In these life situations, which is really elegant,” Zelenitsky continued. “So you should Oviraptor They sit on a clutch of their eggs and actually incubate them. The famous specimen known from Mongolia was the collapsing sand dune, namely Velociraptor And Protoceratops Which are actually physically intertwined and fighting each other.

“However, this specimen from Alberta, preserved in a river environment, gives us a good glimpse into the behavior of Tyrannosaurus, and that is its feeding behavior. That it was a meticulous eater, a picky eater, and it would go after small, fast prey like Setips.

The discovery of the feeding habits of juvenile tyrannosaurs delves into an idea Therrien and Zelentysky have been investigating about how these animals were able to dominate certain ecosystems. They argue that rather than following a single feeding behavior throughout their lives, the diet of these animals changed as they aged – meaning that although they represented only one group of animals, they occupied multiple positions within the food chain.

The stomach contents of Gorgosaurus are preserved in a 75 million-year-old fossil

Bone analysis in Gorgosaurus Stomach contents indicate that he ate two pills Setips A few days before he died.

Image credit: Kohei Tanaka (University of Tsukuba) and François Therin (RTMP)

We know from bite marks on fossil bones that adults were predisposed to eliminating large herbivores such as ceratopsians (horned dinosaurs) and hadrosaurs (duck-billed dinosaurs). grown ups Gorgosaurus Weighing it around 1000 kg (2200 lb) They used their massive skulls and “killer banana” teeth to catch large prey and gnaw through bones — but for a long time, we didn’t know if the young ones (which weighed about a third as much) did the same.

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“Now we have evidence that young dinosaurs had a different diet than adults, we want to try to determine if there are any other things we can say about that, such as what kind of prey they ate, or at what specific timing they did so.” “Diet change, and how,” Therrien said.

“The fact that tyrannosaurs were able to occupy different ecological niches throughout their lives may have been one of the factors that made them such successful animals that they were able to control their ecosystems without leaving room for other types of theropods to come in and try to carve out a niche.”

Occupying different ecological niches would have given Gorgosaurus The benefit of not competing for resources with their older and younger counterparts may have contributed to tyrannosaurs eventually becoming some of the largest predatory dinosaurs in Earth’s history.

The study is published in the journal Advancement of science.

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