Tyrannosaurus rex, the seven-ton, dagger-toothed, Cretaceous-period killing machine, may have had a playful side, according to a University of Kansas paleontologist.
Professor Bruce Rothschild says that the 40-foot predator engaged in play, or at least exhibited behavior consistent with play seen in modern-day animals.
But T. rex didn't fetch sticks or chase Frisbees. Rothschild says that, like a huge kitten, T. rex played with its food – in this case, the carcasses of six-ton ceratopsians, a group of dinosaurs that includes the Triceratops. These terrifying, yet strangely adorable, findings come from Rothschild's examination of fossilized bones found both at feeding sites and in isolation.
Rothschild analyzed a previous study and examined fossils from museum collections, including one at the University of Kansas in Lawrence.
The bones from feeding sites came from the parts of the animals that would have had the most meat. They had the type of tooth marks and broken bones consistent with T. rex's feeding habits. And this dinosaur had a legendary bite: Able to chomp down with nearly 13,000 lbs. of pressure and tear off 500 lbs. of meat with one snap, T. rex had the strongest bite of any land animal.
But the bones found in other, more isolated areas were different. They were from body parts that deliver less nutrition, many of them from ball-shaped bones at the back of the skull called occipital condyles. The bite marks themselves are different as well.
In a paper published in the journal Ethics, Ecology & Evolution Rothschild writes that the pattern of bite marks on these isolated bones are “incompatible with feeding activities, but it characteristic of that found with play by contemporary animals.”
By learning more about how prehistoric animals lived, scientists hope to discover more about how modern animals evolved and how they interact with today's environment.
“Deductive reasoning leads to an alternative explanation,” Rothschild wrote, “Tyrannosaurids played with those bones.”
But not everyone accepts the playful dinosaur hypothesis.
“It's not inconceivable,” says Thomas Holtz, University of Maryland paleontologist, “and in fact we do know that the old warm-blooded biases of biologists who thought birds and mammals played but reptiles didn't is just plain wrong.”
“So there's no reason not to think that any given dinosaur, including T. rex might have played.”
“That said, to then say these … tooth marks necessarily point to or even suggest play behavior rather than anything else is fairly difficult.”
In a phone interview, Dr. Holtz said there are other reasonable explanations for the bite marks.
“It depends on how much of the animal they were eating. Other people have suggested that these tooth marks were not on the parts of the body the T. rex was eating, but as the result of the T. rex. dismembering the animal to get to the tastier parts.”