Dr. Darla Zelenitskaya and Dr. Francois Therrien with their fossil. Photo: Royal Tyrell Museum of Palaeontology/Reuters
Tyrannosaurus rex's last meal was two baby dinosaurs, a study of a 75-million-year-old fossil has revealed.
Its remains were discovered inside a fossil of the extinct predator, shedding new light on its changing diet.
According to a study published in the journal Science Advances, the hind limbs of two small bird-like dinosaurs called citipes were discovered under the rib cage of a juvenile Gorgosaurus, which is closely related to Tyrannosaurus rex.
Research suggests that juvenile Gorgosaurus hunted small juvenile dinosaurs, while earlier fossil evidence showed that adult Gorgosaurus attacked and ate very large herbivorous dinosaurs that lived in herds.
This Gorgosaurus was about seven years old , which was the developmental level of a teenager, and at the time of death he weighed about 330 kg, which is about 10th the weight of an adult.
Tyrannosaurids were large carnivorous dinosaurs that underwent major changes in skull strength and body proportions as they grew.
Dr Darla Zelenitsky, one of the lead scientists on the study, told the BBC the discovery was “compelling proof that tyrannosaurs had changed radically.” their diet” with age.
Dr Zelenitsky said: “We now know that these juveniles (tyrannosaurs) hunted small juvenile dinosaurs. These smaller, immature tyrannosaurs were probably not ready to jump into a group of horned dinosaurs whose adults weighed thousands of kilograms.”
A young Gorgosaurus feeding on its prey. Photo: Royal Tyrrell Museum of Palaeontology/Reuters
The fossil was originally found in the Canadian wilderness of Alberta in 2009, but was buried in rock and took years to prepare for study. Earlier fossil evidence, including bite marks on the bones of larger dinosaurs that match the teeth of tyrannosaurs, has allowed scientists to build a picture of how three-ton adult gorgosaurs attacked and ate very large herbivorous dinosaurs.
Dr. Francois Therrien of The Royal Tyrrell Museum of Paleontology, which is also leading the study, said adult tyrannosaurs were “quite picky eaters.” He told the BBC they were likely to pounce on large prey, “biting through bones and scraping off flesh.”
He added: “The stone inside the chest was removed to expose what was hidden inside. And lo and behold, the complete hind legs of two baby dinosaurs, both less than a year old.”
Dr Zelenitsky said the discovery of “the complete hind legs of two baby dinosaurs, both less than a year old” suggests that this teenage Gorgosaurus “appears I wanted drumsticks – probably because it is the meatiest part.”
She said: “This specimen is unique – it is physical evidence of a completely different feeding strategy for juveniles.”
p>< p>While adults bit and clawed at the killer banana with their powerful teeth, “this animal picked out and even dismembered its prey – biting off the legs and swallowing it whole.”
Professor Steve Brusatte, a paleontologist at the University of Edinburgh and the National Museum of Scotland, said seeing the prey in the dinosaur's guts gave real insight into the animals. He added: “They weren't just monsters, they were real, living beings and quite sophisticated feeders.”