What did the young tyrannosaurs eat? A new discovery by scientists at the University of Calgary in Alberta, Canada, has answered this question.
The discovery was facilitated by the well-preserved remains of Gorgosaurus, which was found to have died between five and seven years old and weighed approximately 334 kilograms.
When the skeleton was examined in the lab, it turned out that among the predator's bones were the bones of its last meal, two specimens of bird-like dinosaurs, known as Citipes.
According to paleontologists, Gorgosaurus was a selective predator, as it limited itself to biting off and swallowing only the shins of its victims without finishing the whole prey.
"It must have killed […] both of these Citipes at different times and then ripped off the hind legs and ate those and left the rest of the carcasses," the research read. "Obviously this teenager had an appetite for drumsticks."
The discovery allowed scientists to better understand how the diet of tyrannosaurids changed with age. Experts believed that the young lizards hunted relatively small and agile prey, such as Citipes. But by age 11, their bodies grew to about 10 meters and weighed more than three tons, after which the giants switched to giant herbivorous dinosaurs.
"This study shows us that tyrannosaurs occupied various ecological niches during their lifespan," the researchers said. "They dominated the niche of mesopredators [mid-size predators] when they were young and then transitioned to apex or top predators as they grew. That is probably the reason why tyrannosaurs were so successful and dominated their ecosystems at the end of the Cretaceous in North America and Asia."
According to paleontologists, such a diet allowed young tyrannosaurids to coexist with adults in a single ecosystem without conflict over prey.
The researchers added that such drastic dietary changes are not uncommon in the animal kingdom, with crocodiles and Komodo dragons eating insects before moving on to rodents and eventually large mammals.