Steak knife teeth made T rex fearsome predators

The dreaded Tyrannosaurus rex and its dinosaur cousins were successful predators partly due to unique teeth designed like steak knives that allowed them to tear through the flesh of their prey, a new study has found.
The study by researchers from the University of Toronto Mississauga (UTM) and colleagues determined that this deeply serrated - or sawlike - tooth structure is uniquely common to carnivorous theropods such as T rex and Allosaurus, and even one of the first theropods, Coelophysis.
Other extinct animals had teeth that were superficially similar, but it was the special arrangement of tissues inside the tooth that strengthened and improved the function of the teeth, researchers said.

The deep serrations made them much more efficient at chomping on bones and ripping flesh of larger animals and reptiles, and allowed them to prosper for about 165 million years as fearsome, top predators.
The only reptile living today that has the same superficial tooth structure is the Komodo dragon, native to Indonesia. It, too, preys on larger animals, researchers said.
"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," said Brink.

She and her colleagues also found that the unique arrangement of tooth tissues did not develop in response to these carnivores chewing hard materials.

They determined this by examining samples of dinosaur teeth that had not yet broken through the gums, as well as samples from mature dinosaur teeth. Unlike humans, reptiles grow new teeth throughout their lifetimes.
"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," said Professor Robert Reisz of the Department of Biology and the UTM vice-principal of graduate studies.
"If you don't cut them right, you don't get the information," Reisz said.

"This brought about a developmental explanation for the tooth formation; the serrations are even more spectacular and permanent," he said.
Brink and colleagues used a scanning electron microscope - a very powerful microscope - and a synchrotron, a microscope that allows the user to understand a substance's chemical composition, to do a thorough examination and analysis of tooth slices from eight carnivorous theropods, including T rex, Allosaurus, Coelophysis and Gorgosaurus.
The study was published in the journal Scientific Reports.