T. rex could be the 'tyrant lizard' after all

"This find, while very novel, does not falsify our work looking at the entire dinosaur fauna of the Hell Creek Formation of eastern Montana where the total number of identified dinosaur skeletons in the field do not support T. rex as an apex predator in this paleocommunity," said Mark Goodwin, an author on that study and a paleontologist at The University of California Museum of Paleontology.

Other research on the topic has also noted that T. rex was too slow and short-armed to be a formidable predator. Based on those findings, another explanation for the rogue tooth is that the hadrosaur was already injured when a hunting-challenged T. rex lunged for it, said Dr. Horner.

“There is no way to determine the fitness of the hadrosaur, nor the way in which the T. rex might have bitten the hadrosaur,” said Horner. “The images leave a lot to the imagination and therefore I'm not even convinced that the T. rex didn't just bite into a dead animal that had a previously healed injury.”

But other evidence suggests that the T. rex was equipped with features that would make it something for other animals to worry about. A 2011 study from The University of Liverpool found that the T. rex had the strongest bite of any known land animal. A separate study from that year, published in PLOS ONE, also found that the dinosaur weighed up to nine tons, revising earlier estimates that had underestimated its terrifying bulk by four or five tons.

The structure of modern ecosystems suggests that T. rex’s enormous size and terrible bite would put it at the top of the food chain, said Burnham.

“There is no modern analog for a large scavenger,” said Burnham, noting that the T. rex has anatomically little in common with modern scavengers, like hyenas and vultures, and much more so with modern predators, like the lion. Small, carnivorous dinosaurs were more likely than the T. rex to have been the scavengers in the Cretaceous-period ecosystem, he said.

“T. rex as a predator is on top of the food chain. T. rex as a scavenger would be at the bottom of the food chain,” he said. “So common sense tells us that it shouldn’t be a scavenger.”

Burnham said that the team is now investigating how the T. rex might have hunted, especially as a small juvenile. One idea is that the juvenile T. rex might have hunted in packs, he said.

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