This new evidence actually came from the fossilized tail bones of a different species, a duck-billed dino called a hadrosaur. When the fossil was dug out of South Dakota's portion of the Hell Creek Formation — a stretch of Earth that runs through Wyoming, Montana, North Dakota and South Dakota, that is rich in dinosaur fossils — the team of paleontologists made a surprising find: there was a large fossilized tooth embedded in the specimen that the researchers were able to identify as the tooth of a Tyrannosaurus rex.
"It's the Holy Grail for a paleontologist," said David Burnham, a paleontologist at the University of Kansas, who co-authored the study on this fossil, according to LiveScience. "Not only was the tooth broken off, but the tail had healed around it. That means that Tyrannosaurus rex attacked that other dinosaur."
This find is significant evidence that T. rex was a predator because finding bite marks on a dead animal just shows that the T. rex ate from that animal; it doesn't show how the animal died. The presence of teeth marks from other types of dinosaurs wouldn't necessarily prove anything, as either type of dino could have brought the animal down and then the other could have scavenged off what was left over. This find, though, shows that a plant-eating dinosaur (therefore not a competitor for prey or carrion) was bitten by a T. rex, and then that dinosaur survived the encounter to live for some time afterwards.
"This is the first time we have physical evidence, and without physical evidence for predation, people always said, 'Oh yeah, T. rex could have been a scavenger,'" Burnham said in the LiveScience article.
The evidence that has spoken up against T. rex's predator status are the structure of its skull, which show that it probably had relatively poor eyesight and a much better sense of smell, which is ideally suited for a carnivore that seeks out rotting carcasses, rather than one that seeks out prey. Also, the T. rex's size and lack of agility would have worked against it when hunting, and its tiny forearms wouldn't have been very good at holding prey.
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Paleontologist Jack Horner, who is not only famous for his work in the field of dinosaur paleontology, but who was technical advisor on the Jurassic Park movies and who wrote the 2009 book How to Build a Dinosaur: Extinction Doesn't Have to Be Forever, isn't convinced of T. rex's predator status yet, though. According to the L.A. Times, Horner said that the hadrosaur may have been lying down when it was 'attacked', since the large tooth was found on the underside of the vertebrae specimen, and once the T. rex realized the animal was still alive, it fled.
However, Robert DePalma, Burnham's graduate student and lead author of the study, disagreed according to the L.A. Times, saying: "A scavenger doesn't come across a food source and realize all of a sudden that it's alive." He also pointed out that the tooth being in the tail of the hadrosaur shows a similarity to how lions hunt, as "they will attack the hindquarters of their victims to immobilize them and then they'll go in for the kill."
Given that evidence was pointing to this massive, fearsome creature being just a scavenger, roaming from rotting corpse to rotting corpse to get its meals, it was probably a bit of a disappointment for paleontologists (and children young and old everywhere). This new evidence reestablishing T. rex's reputation has to be quite welcome.
"It was a very exciting moment," Burnham said. "We felt like the king was back."
(Image courtesy: Wikimedia Commons)
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