Details of the find

The well-preserved fossils are from Gorgosaurus libratus, which lived 76.5 to 75 million years ago in present-day Alberta and Montana. The height of these predators reached 9 meters and their weight was approximately 3,000 kilograms. The history of the bones dates back 75 million years.

This individual probably weighed no more than 350 kilograms, making it 5 to 7 yearswhen he died. This is equivalent to puberty in humans, said study author Darla Zelenicki of the University of Calgary. When he and his colleagues analyzed the fossils, they found small toe bones protruding from the tyrannosaurus’ ribcage. On closer inspection, they found two full pairs of hind legs where the predator’s stomach should have been. The legs belong to Citipes elegans, a dog-sized bird-like dinosaur.

The study’s lead authors next to the entire set of fossils / Photo by Royal Tyrell Museum of Paleontology

Scientists have previously found prey remains in the stomachs of other carnivorous dinosaurs and fossilized food remains of herbivorous dinosaurs. But this is the first time anything has been found in the intestines of a gorgosaurus, and a tyrannosaurus in general. Zelenicki added that this makes the new finding “really exciting.”

In this photo, the ribs of Gorgosaurus are highlighted in green dots and the toes of C. elegans are highlighted in red / Royal Tyrell Museum of Paleontology

The new fossils gave the researchers “the first insight into what was on the menu of young tyrannosaurs; until now we could only guess. The tooth marks left by adult tyrannosaurs on their prey had previously shown that adult predators hunted large prey such as armored herbivores.” platypus dinosaurs.

But juveniles, as we see now, hunted smaller prey because they were much smaller and thinner than adults and had narrower skulls and jaws. This used to be the main theory, but now it has been proven with a fossil example.