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Release from Ohio University:
Brain structure provides the key to
unraveling the function of bizarre dinosaur crests
High-tech imaging reveals inner structure of duck-billed
dinosaur skulls
ATHENS, Ohio (Oct. 9, 2008) — Paleontologists have long
debated the function of the strange, bony crests on the
heads of the duck-billed dinosaurs known as lambeosaurs.
The structures contain incredibly long, convoluted nasal
passages that loop up over the tops of their skulls.
Scientists at the University of Toronto, Ohio University
and Montana State University now have used CT-scanning
to look inside these mysterious crests and reconstruct
the brains and nasal cavities of four different
lambeosaur species. At the annual meeting of the Society
for Vertebrate Paleontology in Cleveland, Ohio, on Oct.
16, the team will present new study findings that
suggest the crests were used for communication.
“The shape of the brain can tell us a lot about what
senses were important in a dinosaur’s everyday life, and
give insight into the function of the crests,” said
study lead author David Evans, a paleontologist at the
Royal Ontario Museum and the University of Toronto.
Some paleontologists have suggested that the crests
heightened the sense of smell by increasing the surface
area of the sensory tissue. Others have argued that they
regulated temperature, and still others have speculated
that the crests acted as sound resonators for
communication.
“It’s difficult to infer the function of structures in
an extinct dinosaur when there is so little resemblance
to any living animal,” said Jack Horner, a member of the
team and paleontologist at Montana State University.
By
using and analyzing CT scans, conducted by Lawrence
Witmer and Ryan Ridgely of Ohio University’s College of
Osteopathic Medicine, the scientists were able to
circumvent the problems of fossilization.
“Even though the soft tissues are not preserved in the
fossils, the shape of the bones that encase the brain
and nasal passages are,” said Evans. “From there, the
anatomy of these missing soft parts is easily
interpreted.”
The CT scan results revealed a mismatch between the
external shape of the crest (which no doubt functioned
as a visual display) and the internal shape of the nasal
passages in closely related species, suggesting a
special function for the nasal cavity. The portion of
the brain responsible for the sense of smell was
relatively small and primitive, indicating that the
crest did not evolve to improve that sense.
Computer models done by other researchers suggest that
the crests could have been used to make low, eerie
bellowing calls that could have been used in
communication, perhaps to call for mates or warn others
of predators. The CT scans documented a delicate inner
ear that confirms that the dinosaurs could hear the
low-frequency calls produced by the crest.
“We were surprised to see just how large the centers of
the brain associated with higher cognitive functions
were,” said Witmer,
Chang
Professor of Paleontology in Ohio University’s College
of Osteopathic Medicine.
“We suspected that the crested duck-billed dinosaurs
used both vocal and visual displays, but now we see that
they had the brain power and hearing to pull off these
behaviors.”
When all the available information is put together,
including the digital brain and ear casts, the
evolutionary relationships of the species, and the
growth pattern of the crest and its high degree of
variability in different co-existing species, it
supports the idea that the elaborate nasal cavity was
likely used to produce sounds for communication. This
study demonstrates the power of using an integrated
approach combining 3D imaging, growth studies, and
phylogenetic sampling to test ideas about the function
and evolution of unusual structures in extinct animals.
The research was funded by the National Science and
Engineering Research Council of Canada and the National
Science Foundation.
This study also will be published in part in an upcoming
issue of the journal The Anatomical Record.
Contact: David Evans can be contacted at:
davide@rom.on.ca,
Ph:
416-586-5753; Lawrence Witmer can be contacted at
witmerL@ohio.edu, Ph: 740-593-9489.
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