A new discovery has provided the best evidence yet for the theory that tyrannosauruses ate each other. It seems that when it comes to gnawing on each other’s bones, the dinosaur world hosted a repeat offender.
The first evidence that these fearsome beasts made no exceptions for their own kind emerged five years ago, based on tooth marks on Tyrannosaurus rex bones from a time and place where there are thought to have been no other carnivorous species large enough to have left them.
Interest in the idea was so high that a study to investigate was crowdfunded, and earlier this year similar signs were found on a Daspletosaurus specimen, a predecessor to T rex by about 10 million years. Nevertheless, in that case the dinosaur responsible, while almost certainly still a tyrannosaur, could have been a gorgosaurus, not just a different species, but a different genus and subfamily. Not much of a relative at all really.
Now Matthew McLain, a PhD student at Loma Linda University, California, has added further evidence, and it looks like the jury is ready to convict. Presenting at the Geological Society of America’s conference in Baltimore, McLain announced the finding of a tyrannosaur bone from the Lance Formation, Wyoming, covered in “very deep grooves.”
These grooves were made by a large animal pulling flesh away from the bone the way humans do to chicken bones. Most could have been made by a number of terrifying creatures of the era, but one groove shows distinctive signs of being the legacy of a tyrannosaur. The maker appears to have turned its head while feeding, and the groove shows signs of a serrated tooth.
The only two suspects in the area at the time with the means to make such marks were Tyrannosaurus rex or Nanotyrannus lancensis, McLain reports. Motivation isn’t too hard to come by either, since it must have taken a lot of food to keep a six tonne predator on the go, and one of its kind would be a handy source of protein in the likely event that ethics weren't its thing.
"This has to be a tyrannosaur," said McLain in the statement. "There's just nothing else that has such big teeth." To be fair, the bite marks indicate that the unfortunate dinner was already dead when the munching was occurring, so we can’t tell if it was killed by a cousin, or died some other way and no one wanted to let a meal go to waste.
The grooves that could convict a cannibal. Credit: Matthew McLain.
McLain hopes to calculate the size of the teeth responsible, and use this to convict the exact species, but the question may be moot. Paleontologists continue to debate whether N lancensis really existed, or if the few specimens that have been found were actually juvenile T rex dinosaurs.
Given the popular image of T. rex as a lone hunter with few social skills, it might not seem surprising that it ate its own kind. However, this image may be inaccurate, with a set of footprints suggesting at least some tyrannosaur species hung together.
Plot idea for future Jurassic Park sequels: a herd (or terror) of tyrannosaurs eat everything in sight until they run out of food and turn on each other.