The
assignment was to write a short piece based on an article from Science. It was
completed from the first encounter with the article in about an hour and a
half.
The
familiar dinosaur faces of books and movies may have to be redrawn, showing
once again the challenge of speculating about extinct animals from their fossil
remains.
Research reported in the August 3 issue of the journal Science suggests that dinosaur nostrils were near the tip of the dinosaur snout, rather than farther back as usually assumed.
The
confusion arises because the fleshy opening that we call a nostril is not
preserved in fossils. The underlying cavity in the skull, which is preserved,
covers a large fraction of the head in dinosaurs. In the past, the nostril has
been placed near the rear of this cavity, in part because the large, sauropod
dinosaurs were at first thought to live in water. Indeed, the nostril of Diplodocus was placed on the top of the
head, where it could serve as a snorkel.
Although sauropods have for several decades been seen as land
creatures, the nostril has remained in the back of the nasal cavity. In the
current study, Lawrence M. Witmer of
First,
Witmer looked at the nostrils of 62 different species, including birds and
alligators, some of the closest living relatives of dinosaurs. After marking
the nostril with a special paint, he used x-ray images to locate the nostril relative
to the underlying bony cavity.
In almost
all cases, the nostril was close to the front edge of the cavity. Indeed, in some
distant species, like humans, the nostril is beyond the front of the cavity,
with the help of cartilage. The simplest assumption is that dinosaur nostrils
were also near the front.
In
addition, Witmer observed in dinosaurs, near the expected forward nostril position,
signs in the fossilized bone of a high density of blood vessels. In related
species, such blood vessels support a special structure found close to the nostril.
Second, Witmer argued that having the nostril at the rear simply makes
no sense. To smell danger or food, the nasal opening should be as far forward
as possible, while to assist in taste it should be close to the mouth. Moreover,
for air to be heated and moistened, it must flow over the nasal tissues. If the
nostril were at the rear, most of the cavity would simply be a dead end. Thus
the position of the nostril may play an important role in the temperature
regulation of dinosaurs, a topic of active debate.
An
accompanying article in Science quoted Christopher Brochu,
a paleontologist from the
© 2003 Don Monroe