The well-preserved last meal of a fossilized dinosaur from approximately 75 million years ago in its stomach reveals surprising details about its diet. A juvenile Gorgosaurus libratus (a type of tyrannosaurus) was found with the hind legs of small bird-like dinosaurs in its stomach, according to University of Calgary researchers.

Tyrannosaurs, which include Gorgosaurus and the more famous tyrannosaurus, were among the most fearsome predators of their time. Current evidence shows that older tyrannosaurs generally ate large herbivores, the researchers said. But the latest discovery shows that as these species grow, their diets change, too, according to a study published in the journal Science Advances.

“This is the first time such well-preserved stomach contents have been found in the skeleton of a large tyrannosaur species,” said study co-author Darla Zelenicki.

The creature weighed over 700 pounds (only 10% of the weight of an adult) and was thought to have died young, between five and seven years old. The fossil was first found in Dinosaur Provincial Park in Canada in 2009. Museum staff noticed the toe bones in the dinosaur’s belly for the first time. Researchers determined that these were the remains of sitips, small dinosaurs the size of turkeys.

“The stone in the chest was removed to reveal what was hidden within. Lo and behold, in the stomach were the entire hind legs of two baby dinosaurs, both less than a year old,” says Francois Therrien, one of the study’s authors.

It turns out that there are two different sets of legs eaten at different times, determined by their different levels of digestion. According to the researchers, the dinosaur probably chose to eat the hind legs because they would be the meatiest part of the body.

“It is well known that tyrannosaurs changed a lot during growth, from slender forms to robust dinosaurs with crunching bones, and we know that this change was related to feeding behavior,” Zelenitskyi said. said.

“They appear to have transitioned from hunting prey such as Citipes that were a fraction of their size at a young age to hunting megaherbivorous dinosaurs as large or larger than their own size as adults,” he said.

The discovery shows that juvenile tyrannosaurs, with their narrow skulls and blade-like teeth, were better at eating smaller prey, while adult tyrannosaurs’ larger skulls and powerful teeth meant they could eat much larger prey.