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Tyrannosaurs "chewed" their food
From: Ben Creisler firstname.lastname@example.org
Tyrannosaurs chewed their food
In case the following story has not been mentioned here in
all the excitement about tyrannosauroid feathers:
Researchers Take a Bite Out of Tyrannosaurid Eating Theory
A close look at the teeth of tyrannosaurids revealed to
University of Arkansas researchers that these large
carnivores may have eaten more like mammals than their
reptilian cousins - by slicing and processing food with
their teeth before swallowing it down.
Newswise - Popular movies have shown Tyrannosaurus rex
snapping up prey and swallowing it in great, ghastly
gulps. But a close look at the teeth of tyrannosaurids
revealed to University of Arkansas researchers that these
large carnivores may have eaten more like mammals than
their reptilian cousins - by slicing and processing food
with their teeth before swallowing it down. This is the
first time researchers have documented reptilians with
eating habits that more closely resemble those of a mammal.
University of Arkansas anthropology professor Peter Ungar
and former graduate student Blaine Schubert worked
together under a grant from the Jurassic Foundation to
reconstruct the diets of tyrannosaurids. These giant
carnivores - classified as reptilians, a term that
encompasses both bird and reptile species - could have
been scavengers or hunters. Ungar and Schubert originally
started their research to settle that question.
In the process, however, Ungar and Schubert uncovered
evidence that tyrannosaurids may have processed their food
like mammals, rather than swallowing it whole like other
reptilians. A paper detailing their findings has been
accepted for publication in an upcoming issue of Acta
Palaeontologica Polonica (APP), a paleontology journal
headquartered in Poland.
Modern reptilians eat differently from mammals, the
researchers explained. For the most part, they swallow
food whole, without chewing. They don?t have the same
degree of muscle differentiation and jaw control that
?They use their teeth to kill and capture animals, or to
pull plant material into the mouth,? Ungar said. ?They
don?t break stuff down in the mouth at all. All digestion
happens inside the body.?
Mammals, on the other hand, have complex jaw joints and
well-separated jaw muscles, with teeth of different shapes
to allow precise chewing. The act of chewing starts the
digestion process by breaking the food down to be digested
further in the stomach.
?Mammals start with a big chunk of food and end up with
lots of little pieces,? Ungar said.
Reptilians and mammals process their food differently
because they must maintain different metabolic rates.
Reptilians are cold-blooded and rely on the sun to heat
them so they can function. Because they don?t derive their
own heat, their metabolic rate is about one-tenth that of
?They don?t require the same amount of energy from food to
function,? Ungar said.
As warm-blooded creatures, mammals have to increase the
efficiency with which their bodies break down food. Part
of that process involves breaking food down in the mouth
so stomach acids can work on it more quickly, and the body
can get more nutrients from it.
Scientists have yet to determine conclusively whether
dinosaurs were warm-blooded or cold-blooded creatures.
Since tyrannosaurids are reptilians, however, logic would
seem to dictate that they would swallow their food whole.
?This makes me pause and say ?Wow they?re breaking things
apart in the mouth.? They?re either eating something big
or eating something more efficiently,? Ungar
said. ?They?re doing something different than what the
typical crocodile does, for whatever reason.?
Ungar and Schubert started their research at the Museum of
Natural History in Gainesville, Fla., where they studied
the teeth of modern reptilians, including caimans, iguanas
and Komodo dragons. They used microscopy to look at the
scratches, pits and grooves on the teeth and compared
these wear features to the known diets of the reptilians.
None of the modern reptilian teeth showed the tell-tale
wear facets that occur with tooth-to-tooth contact,
indicating that the reptilians were not using their teeth
to process food before swallowing.
Next Ungar and Schubert?s research took them to the Royal
Tyrrell Museum of Palaeontology in Alberta, where they
took high-resolution impressions of tyrannosaurid teeth.
On these teeth, the researchers found wear facets with
microscopic scratches all running in the same direction -
something before only found in mammals.
?We believe at least some of these facets indicate tooth-
to-tooth contact,? Ungar said. ?It?s intriguing because
the tyrannosaurids are the only group of reptilians we?ve
seen this in.?
?We are now excited about looking for similar patterns in
other carnivorous dinosaurs,? added Schubert.
Ungar and Schubert?s findings indicate that T-rex and
other tyrannosaurids may have adapted specific physical
features for slicing flesh. Other meat-eating dinosaurs
don?t show the same features, making tyrannosaurids a
Ungar and Schubert?s research was just the first step in
determining that they may have processed their food
differently. Next, they plan to test the hypothesis that
these creatures were specialized, bone-crushing carnivores.
?We?re looking at years of further research,? Ungar said.