In the annals of prehistory, one of the best titles of all is “Tyrannosaur.” The moniker perfectly describes the immense, toothy carnivores that ruled the northern hemisphere during the Late Cretaceous – the largest predators ever to stalk the land. And, as you might expect from true tyrants, they didn’t get along very well with each other. A skeleton described by palaeontologists David Hone and Darren Tanke illustrates in painful detail how these dinosaurs suffered at each others’ jaws.
The specimen – found in 1994 and cataloged as TMP 1994.143.0001 – belonged to a subadult Daspletosaurus that roamed southeastern Alberta around 73 million years ago. It’s not the prettiest skeleton ever found. The dinosaur’s bones drifted from each other after death, and some were lost to erosion before Philip Currie discovered it. But it isn’t the completeness of this tyrannosaur that makes it remarkable. It’s the peculiar damage that can be seen on the tyrant’s bones.
The dinosaur’s skull tells the tale. Patches of healed and damaged bone show where the young tyrannosaur was bitten on different occasions, Hone and Tanke write, from the tip of the snout, along the jaws and cheek, to the back of the skull. The Daspletosaurus survived these wounds long enough to heal, but clearly this dinosaur got into plenty of scraps. This seems typical of tyrannosaurs and other large predatory dinosaurs – several fossils have previously been described with healed bite wounds to the face. When you’ve got small arms, literally fighting face-to-face is the best option. But who was the Daspletosaurus tussling with?
Daspletosaurus wasn’t the only tyrannosaur found in the 73 million year old rock of Alberta. The more slender Gorgosaurus inhabited the same environment, and has been raised as a suspect in cross-species fights before. Then again, the Daspletosaurus could have been battling with members of its own species. Being that we’re far too late to watch these Mesozoic martial arts contests, the best we can do is narrow down the identity of the opponents to “other tyrannosaurs.” Just imagine the shrieks and bellows as these apex predators faced off against each other.
But that’s not all. Hone and Tanke have also documented “fresh” bite marks on the Daspletosaurus skull – that is, bite wounds that never healed. Such damage indicates that something fed on the Daspletosaurus after it died, and, as before, the best candidate is another tyrannosaur. Closely-spaced bite marks on the dinosaur’s jaw, in particular, seem to show that another tyrant came along and scraped off muscle from the body using its small front teeth. If this is the hallmark of another Daspletosaurus, then, like Tyrannosaurus, it was a cannibal. And who could blame the dinosaur? At the end of the day, meat is meat. Clearly, the Cretaceous was a tyrannosaur-eat-tyrannosaur world.
For more on prehistoric bite marks, check out our latest video with palaeontologist Stephanie Drumheller-Horton!
Hone, D., Tanke, D. 2015. Pre- and postmortem tyrannosaurid bite marks on the remains of Daspletosaurus (Tyrannosaurinae: Theropoda) from Dinosaur Provincial Park, Alberta, Canada. PeerJ. doi: 10.7717/peerj.885