The two possible explanations for what happened to an Albertosaurus after its death near Drumheller are wildly divergent.
According to a new study by paleontology master’s student Joshua Doyon, the more likely account is that this eight-year-old, “teenage” cousin of the Tyrannosaurus rex died of unknown causes, and shortly afterwards became dinner for a dromaeosaurid or “raptor,” the group of small carnivorous dinosaurs made famous by Jurassic Park. The study, published in the Journal of Paleontology, is the first evidence of a raptor feeding or scavenging on a tyrannosaur, pointing to a more complex food web in the dinosaur ecosystem than previously thought.
“This turns everything on its head, because you’re dealing with a very small dinosaur eating a very big, mean, nasty dinosaur like a tyrannosaur,” says Philip Currie, the U of A’s lead paleontologist and Doyon's supervisor.
The more unlikely hypothesis is no less dramatic, says Doyon, judging by the distance between tooth marks on the Albertosaurus' jaw, which can be matched to the teeth of dinosaurs known to roam Alberta's prehistoric ecosystem. If the culprit isn't a raptor, the only other suspect is a baby Albertosaurus, he says.
“If it is a young Albertosaurus, this would be an event of cannibalism — by a baby, about two metres long, eating a larger sub-adult,” estimated to be about six metres long and weighing 530 kilograms.
The Albertosaurus, or “Alberta lizard,” was the apex predator in what is now Alberta during the Late Cretaceous period, about 73 to 67 million years ago. It was named the year Alberta became a province in 1905, and Doyon's specimen — a scattered collection of skull fragments — was found and reported by a member of the public in 2022. It was collected and prepared by the Royal Tyrrell Museum, whose technicians found what they suspected were tooth marks and forwarded to the U of A for further analysis.
Starting as an undergraduate, Doyon meticulously studied the tooth marks on the jaw bones, systematically eliminating possible trace makers until there were few left. Because there is no sign of bone healing, it is likely the marks were made around the time of death or afterwards, indicating feeding or scavenging, he says.
The publication marks a huge step in Doyon’s academic journey.
“We are lucky to be able to get involved in research so early in our careers,” he says, noting the U of A’s proximity to the badlands and the Royal Tyrrell Museum — as well as access to the university’s extensive collection of dinosaur specimens.