About 75 million years ago, a towering tyrannosaur may have lit into one of its own species, ripping into its skull and leaving behind jagged scars and deep punctures that have only recently seen the light of day.
The beastly tale comes from paleontologists examining the marred skull of the possible dinosaur victim, which itself was a teenage tyrannosaur. Even so, scientists not involved in this study warrant caution in such interpretations, noting the difficulty of pinning ancient crimes on any one genus without more evidence.
Researchers originally discovered the dinosaur skull in 1994 in Dinosaur Provincial Park in Alberta, Canada. An analysis showed the bones belonged to Daspletosaurus, a genus of tyrannosaur — a group of carnivorous, bipedal dinosaurs with deep jaws and short arms that includes the notorious Tyrannosaurus rex. [See Amazing Illustrations and Photos of Daspletosaurus]
Although paleontologists examined the Daspletosaurus specimen after its excavation, the researchers of the new study are the first to do an in-depth analysis of its skull marks, said the study's lead researcher, Dave Hone, a lecturer in zoology at Queen Mary University of London.
The roughly 22-inch-long (55-centimeter-long) Daspletosaurus skull wasn't fully grown, and likely belonged to a subadult, the equivalent of an older teenager in human terms, Home said. When it died during the Late Cretaceous, its entire body measured just less than 20 feet (6 meters) long and weighed about 1,100 pounds (500 kilograms), he added.
The researchers found a number of healed skull injuries. Several, including a circular puncture on the back of the skull, are similar in size and shape to tyrannosaur teeth, they said.
Hone and his colleagues suggest that another Daspletosaurus injured the specimen, largely because the genus was the only other large carnivore around in that period besides crocodilians, prehistoric relatives of crocodiles. But crocodilians found in the same rock formation as the dinosaur tend to be small, and are "unlikely to have left such large marks," the researchers wrote in the study.
It's also thought that crocodilians tended to bite and twist, and there isn't evidence of that on the Daspletosaurus skull, Hone said.
Other experts say the study makes a strong case for such aggressive behavior, but insist it's impossible to know what creatures may have injured the Daspletosaurus.
The study was published on Thursday in the journal PeerJ.