Toothy terror: dinosaurs like T. rex had unique serrated teeth

By Will Dunham
WASHINGTON, July 28 (Reuters) - If you want to know the
secret behind the success of Tyrannosaurus rex and its
meat-eating dinosaur cousins, look no further than their teeth.
Scientists on Tuesday unveiled a comprehensive analysis of
the teeth of the group of carnivorous dinosaurs called
theropods, detailing a unique serrated structure that let them
chomp efficiently through the flesh and bones of large prey.
Theropods included the largest land predators in Earth's
history. They first appeared about 200 million years ago and
were the dominant terrestrial meat-eaters until the age of
dinosaurs ended about 65 million years ago.
The study involving eight theropod species revealed their
previously unknown tooth complexity. Internal dental tissues
were arranged in a way that reinforced the strength and
prolonged the life of teeth that were serrated like steak knives
for easy dismembering of other dinosaurs.
University of Toronto Mississauga paleontologist Kirstin
Brink said fossil evidence showed that T. rex's teeth could
crush bone. Its teeth have been found embedded in the bones of
its prey and chunks of bone appear in its fossilized dung.
"But the serrations were most efficient for piercing flesh
and gripping it while ripping off a chunk of meat, called the
'puncture and pull' feeding style," Brink said.
The researchers analyzed slices from fossil teeth using a
powerful microscope and a sophisticated device that revealed
tooth chemical properties.
They studied teeth from: the early and relatively small
Coelophysis; bird-like Troodon; large predators Allosaurus,
Gorgosaurus, Daspletosaurus, Tyrannosaurus and
Carcharodontosaurus; and big, semi-aquatic Spinosaurus.
The teeth of Tyrannosaurus and Carcharodontosaurus measured
up to 9 inches (23 cm) long.
"In theropods, the serrations are larger and deeper than the
superficial view suggests, making them stronger and longer
lasting, less likely to get damaged or worn," University of
Toronto Mississauga paleontology professor Robert Reisz said.
Dinosaurs were able to continuously grow teeth throughout
their lives. When a tooth was broken, another could replace it.
"It could take up to two years for a tooth to grow back in
the big theropods like T. rex. Therefore, having specially
reinforced teeth means less tooth breakage and less gaps in the
jaw, leading to more efficient eating," Brink said.
The Komodo dragon, a lizard up to 10 feet (3 meters) long
from Indonesia, is the only living reptile with serrated teeth
closely resembling those of theropods although these teeth
evolved independently of those of the dinosaurs, Brink said.
The research appears in the journal Scientific Reports.