Date: August 25, 2016
Source: University of Toronto]
Imagine how much dental care
you'd need if you had 300 or more teeth packed together on each side of your
mouth.
Duck-billed dinosaurs
(hadrosaurs), who lived in the Cretaceous period between 90 million and 65
million years ago, sported this unique dental system, which had never been
fully understood until it was examined at the microscopic level through recent
research conducted by Aaron LeBlanc, a University of Toronto Mississauga PhD
candidate; his supervisor, Professor Robert Reisz, the University of Toronto
Mississauga vice-dean, graduate, and colleagues at the Royal Ontario Museum and
the Museum of the Rockies.
Rather than shedding teeth and
replacing them with new ones like other reptiles, hadrosaurs' mouths contain
several parallel stacks of six or more teeth apiece, forming a "highly
dynamic network" of teeth that was used to grind and shear tough plant
material. Although hadrosaur teeth appear to be fused in place, LeBlanc and his
colleagues show that the newest teeth were constantly pushed towards the
chewing surface by a complex set of ligaments. When viewed under the
microscope, the columns of teeth are not physically touching and are held
together by the sand and mud that can get in between the teeth following the
decay of the soft ligaments after the animals died.
"Hadrosaur teeth are
actually similar to what we have because our teeth are not solidly attached to
our jaws. Like us, hadrosaur teeth would have had some fine-scale mobility as
they chewed thanks to this ligament system that suspended the teeth in
place," says Reisz.
As they reached the grinding
surface, hadrosaur teeth were essentially dead, filled with hard tissue --
unlike humans, whose teeth have an inner core filled with blood vessels and
nerves.
"Since the teeth were
already dead, they could be ground down to little nubbins," Reisz says.
LeBlanc says this tooth structure
-- with its tough grinding surface -- was "well-adapted to break down
tough plant material for digestion," through both shearing and grinding.
This adaptation may have contributed to the hadrosaurs' longevity and
proliferation.
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