With only bones for clues, scientists continue
to puzzle over many details of dinosaur
appearances and physiology. Detective
work by a paleontologist at Ohio University
now indicates that the creatures' fleshy
nasal passages were larger than had been
thought, which could lead to more-realistic
depictions and greater understanding of
their respiratory functions.
In the August 3 issue of the journal Science,
National Science Foundation (NSF)-supported
researcher Lawrence Witmer reveals that
nostrils on many dinosaurs were much farther
from the eyes and closer to the mouths
than previously depicted. By comparing
telltale markings on bones from their
present-day relatives, he has shown that
many dinosaurs had large nasal passages
that might have been important for heat
exchange and other key physiological processes.
Witmer is an associate professor of biomedical
sciences and an anatomist in the university's
College of Osteopathic Medicine. X-ray
examinations of skulls from more than
65 surviving dinosaur relatives - including
crocodiles, birds and lizards - helped
him infer the probable location of cartilage,
blood vessels and other soft tissues that
made up the extinct creatures' nasal cavities.
He discovered that nearly all animals share
these traits, which gives weight to his
assertion that previous depictions of
dinosaur nostrils were inaccurate.
"Our findings were consistent, even in
turtles and mammals," Witmer said. "We
saw an unusual commonality of how the
nasal components relate and are positioned.
It turns out that the nostril positioning
applies to almost all animals."
As a result, scientists may have to change
the conventional view of dinosaur nostrils,
which have until now been based on the
placement of cranial cavities near the
eye sockets. Witmer found the largest
nasal passages in horned dinosaurs like
Triceratops, duck-billed dinosaurs,
and brontosaurs like Diplodocus,
the latter of which was 80 to 90 feet
long and weighed more than 40 tons.
Other scientists had studied dinosaur noses,
Witmer said, but their focus was primarily
on olfactory functions. He isn't only
interested in how the animals were able
to smell; his main goal is understanding
overall dinosaur physiology. As his research
progressed, Witmer was surprised to learn
that no one had previously examined the
position of nostrils.
"Learning the biological rules for assembling
the bones of extinct animals, like dinosaurs,
is notoriously hard," said Jack Hayes,
NSF program director for ecological and
evolutionary physiology. "But learning
the rules for how to place the rest of
the animal on those bones may be even
harder. Because both the general public
and many biologists are keenly interested
in dinosaurs, new tools for reconstructing
the anatomy and biology of dinosaurs are
valuable. What's exciting about Witmer's
findings is that they may make it possible
to explore the function of dinosaur respiratory
systems in more detail."
This rendering reflects the new position
of the nostrils on the sauropod dinosaur
Diplodocus (left and bottom right).
Top right is the skull of Diplodocus;
middle right is the traditional view with
the nostril located more to the rear of
the head, which has been refuted by the
new research by Ohio University's Lawrence
A larger version
Copyright Science/Paintings by
M. W. Skrepnick under the direction of
L. M. Witmer
Ohio University paleontologist Lawrence
Photo by: Jo McCulty.
Changing nostril position in Tyrannosaurus
rex. The middle image is the traditional
view with the nostril located more to
the rear of the head. The image at lower
right is a new restoration based on Witmer's
study reflecting the forward position
of the nostril. The image at upper left
is the skull.
A larger version is
Copyright Science/Paintings by
W. L. Parsons under the direction of L.
Note to Editors