If you think adolescents can be scary, you should have met Tyrannosaurus rex.
Somewhere around 70 million years ago, a young T. rex was wandering through what is now the badlands of southeastern Montana when it happened upon another youngster, possibly a member of its own family.
There ensued a mighty battle, and when it was over, the wandering T. rex had four puncture wounds through its skull. It survived the fight, and largely recovered from the wounds, only to die a few years later of unknown causes.
The bipedal dinosaur, known these days as "Jane," was only 12 or 13 years old when the mud entombed her bones and preserved the story of her brief life for scientists who would pass her way in 2001.
It's a remarkable story, because few nearly-complete skeletons of juvenile dinosaurs have been found, and virtually none revealed as much about the lifestyle of these huge beasts as Jane is telling from her new home in the Burpee Museum of Natural History in Rockford, Ill. In the beginning, no one was even sure what she was.
"Nobody had ever found a juvenile T. rex skeleton before," Joe Peterson, lead author of a study in the current issue of the journal Palaios, said in a telephone interview. Peterson, a geologist with Northern Illinois University in DeKalb, was a student when he began helping scientists from NIU carefully excavate the bones that are now known as "Jane," although no one knows if the skeleton is a male or female.
For the first few years, no one paid any attention to the puncture wounds in her skull, because they were too busy trying to figure out what she was in the first place.
"There was a big picture debate going on about the identity crisis of this 70-million-year-old specimen," Peterson said. But once that debate simmered down, he said, they made the "cool" discovery of wounds that had healed over.
"It's very rare to find a juvenile, but to find one with really good evidence of behavior is even more exciting and rare," Peterson said.
So what really happened to Jane? It seemed unlikely that she would have fought with another adolescent T. rex. She was too young to mate, so sexual conflict probably wasn't the cause. And at first it didn't seem likely that two kids would have had such a fierce fight.
But one by one, other options were eliminated. The wounds couldn't have been left by one of the crocodiles that inhabited the same area. Crocs leave very distinct wounds, and there was no sign of the death roll that crocodiles use to thrash their prey.
And it couldn't have been an adult T. rex.
"If an adult had bitten Jane on the face, Jane wouldn't have a face," Peterson said. "You could fit Jane's entire head in an adult T. rex's mouth. It would have crushed the head completely."
An adult T. rex could be up to 43 feet in length, about twice the size of Jane. Jane would have weighed only 1,500 pounds compared to the Field Museum's famous Sue, the largest T. rex ever found, who weighed nearly six tons. Jane's teeth were small and elliptical, probably used to strip meat from a bone.
An adult's teeth are "kind of banana-sized," Peterson said, and were used to crush, not cut.
Then the scientists came up with the smoking gun. Jane's own teeth fit perfectly into the puncture wounds in her own head.
"It's impossible for her to bite herself on her face, so it seems likely it was another juvenile," Peterson concluded.