T. rex and its ilk owed hunting success to special serrated teeth

Many extinct creatures, including killer theropod dinosaurs like the notorious Tyrannosaurus rex, had serrated teeth, with jagged cutting edges to help them chew through flesh. Some years ago scientists noticed that theropods also had some unusual structures inside their teeth: interconnected cracks and voids that many thought must have been wear and tear from the act of eating hard stuff, like bones.

But new research, published Tuesday in the journal Scientific Reports, proposes another explanation for those structures -- that they were present in teeth before they even erupted from dinosaurs' gums, and that they played a key role in maintaining the fearsome, knife-like serrated edge of the animals' bite.

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FOR THE RECORD

An earlier version of this article said that a synchrotron was a microscope. A synchrotron is an instrument used in conjunction with microscopic analysis.

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The discovery sheds light on the evolution of theropods and how they were able to thrive on Earth as an apex predator for 165 million years.

"All animal teeth are made from the same building blocks, but the way the blocks fit together to form the structure of the tooth greatly affects how that animal processes food," said study first author and University of Toronto Mississauga postdoctoral researcher Kirsten Brink, in a statement. "The hidden complexity of the tooth structure in theropods suggests that they were more efficient at handling prey than previously thought, likely contributing to their success."

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To conduct their experiment, Brink and her co-authors used a powerful scanning electron microscope and a synchrotron and spectroscope (devices used to help analyze chemical composition) to examine thin tooth slices from eight carnivorous theropods (including a T. rex) and from other ziphodont, or serrated teethed, animals (including an extinct shark and a Komodo dragon.)

Looking at erupted and unerupted teeth, they found that the unique internal structure was unique to the theropods.

Study co-author Robert Reisz, a biologist at the University of Toronto Mississauga, said that completing the research had been a technical challenge.

"What is startling and amazing about this work is that Kirstin was able to take teeth with these steak knife-like serrations and find a way to make cuts to obtain sections along the cutting edge of these teeth," he said. "If you don't cut them right, you don't get the information."

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