Amazing discovery: They found a fossil of a tyrannosaur with traces of its last meal preserved in its stomach

Unlike their massive adult relatives at the top of the food chain, it seems that way Dinosaurs Juveniles had to rely on prey more suitable for their smaller, more flexible build.

Sometimes that meant a variety of little things Dinosaurs They resemble birds, which were apparently so abundant that small predators selected and ate their fleshy hind legs, leaving the rest for scavengers. The researchers announced that the main dish was on the menu Late Cretaceous period In a study just published in the journal Advancement of science.

How did scientists know the elements of the diet 75 million years ago? In the Formation of a dinosaur park in AlbertaCanada, an amazing first fossil was discovered: A Skeleton of a young GorgosaurusFortunately he was preserved with his last two meals in the stomach cavity. Each feast included a pair of hind legs severed from small, bird-like dinosaurs (of the species Citipes elegans). The little dinosaur tore off its legs and swallowed them whole.

Reveals each pair of legs Different levels of digestion On the surfaces of the bones, indicating that they were consumed during two different meals a few hours or days apart.

This unique discovery provides compelling evidence for a long-standing hypothesis: as they grow, LDinosaurs adapted to hunt and eat different types of prey During the different stages of their lives. Juveniles can run, kill, and subsist on animals such as the smaller setips.

Once they reached adult size, they hunted equally large prey among the massive herbivores of the Late Cretaceous, such as duck-billed and horned dinosaurs. This is the first evidence that tyrannosaurs radically changed their diet as they transitioned from adolescence to adulthood, something that had long been suspected based on their skeletons.

Dinosaurs are known to be huge and fearsome predators like Tyrannosaurus Tyrannosaurus rexWhich can weigh up to eight tons and be up to 40 feet long.

Of course, they didn’t start out like that. The babies were probably the size of a Border Collie, and throughout their lives they went through significant changes not only in size, but also in physiology. Younger tyrannosaurs were smaller and more flexible, with narrow skulls and razor-like teeth, which were key to catching, dismembering and devouring small prey. On the other hand, the massive, broad skulls and giant teeth that evolved in adults were better suited to chewing much larger prey and crushing and gnawing bones.

The caloric values ​​of small prey may not have been worth it for such large adult predators, if they were still able to catch them after losing some speed and agility with size and age.

Today’s crocodiles and Komodo dragons undergo similar nutritional changes as they grow. he Gorgosaurus libratus The fossilized juvenile or adolescent was between 5 and 7 years old, and was measured roughly as tall as the human at the hips, and was approximately 4 meters tall. It probably weighed about 700 pounds, but even at that weight it was less than 15 percent the size of its adult relatives and had a lot of growing to do.

The two small, bird-like chicks he ate probably weighed 20 to 30 pounds, about the size of male wild turkeys. But outwardly it looked more like an emu or a cassowary. They would have been among the fastest runners in the ecosystem, like juvenile dinosaurs. These setips may have given the juvenile an opportunity to catch its prey.

Gorgosaurus is a large species of predatory dinosaur found in the famous Dinosaur Provincial Park ecosystem dating back 75 to 80 million years.

Over the years, more than 50 species of dinosaurs have been identified there, as well as many other mammals, birds and reptiles. Few of those fossil finds rival the adolescent Gorgosaurus.

In 2009, Darren Tank, head coach of the team Royal Tyrrell MuseumThe amazing fossil was found in the badlands of Dinosaur Provincial Park. The discovery was exciting. Fossilized skeletons of young tyrannosaurids are much rarer than those of their adult relatives. Larger creatures with stronger skulls and bones survived the fossilization process in the region better than more fragile juveniles.

But as he prepared the fossil, it soon became clear that it was more than it first seemed. Tanki noticed small toe bones that were not close to the animal’s legs. They were too small to belong to this dinosaur and came out of the rib cage from inside the animal. Since then, the team has slowly examined the fossil from the inside out to find out what was behind the rib cage.

a job Detective It led to more serendipitous results. Most species are identified by their skulls, but these predators have survived only with torn off legs and feet. Fortunately, Setipes was only identified from previously collected foot bones, which matched fossils excavated from the ancient stomach cavity.

Amazingly, four legs found here represent the most complete setaeus skeleton ever, preserved because they were swallowed by the dinosaur and the stomach protected the bones from prey.

Stomach contents of this type are rare and usually found among small, fully fossilized animals, such as the Oviraptor Veloceratops specimen that had a lizard in its stomach. Big dinosaurs are a different story. In the past, when something was still found in a dinosaur’s belly or in a dinosaur’s coprolite, it was crushed bone.

In the absence of stomach contents, paleontologists had to learn more about… Diet Dinosaur by other means. Researchers are looking for fossil bones with bite or puncture marks, which may have been caused solely by T. rex teeth. If such wounds showed signs of healing, they were likely caused by predators attacking live prey, rather than by scavenging, although the animals did many things both. The discovery of dinosaur droppings reveals more evidence.

the Adult and juvenile tyrannosaurs are so physically different that they are almost like two different animals.. The smaller, lighter hatchlings with long, slender legs were likely agile and fast runners without significant biting force. As they grow, around 11 years of age, the animals’ size and functions change dramatically. Adults had massive skulls and significantly stronger bite force. As predators and scavengers, adult fish feed indiscriminately on all parts of the carcass, crushing bones and swallowing animals whole.

Because of these differences, scientists suspected that the juveniles were unsuccessful at hunting giant herbivores, but researchers did not know exactly what the animals ate. This fossil provides evidence that it fed on small species of dinosaurs, as well as on other small ones; These individuals he ingested were one year old. Furthermore, it selectively selects only the fleshy hind legs to eat. This shows that at least this specimen not only fed on different animals than adults, but also did so in a different way.

* Darla Zelenitsky is a paleontologist at the University of Calgary