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Examples of periosteal reactive bone in selected specimens of Triceratops. Arrows indicate lesions on (A) the left jugal of YPM 1822 (Yale Peabody Museum, New Haven, Connecticut, USA) and (B) the right squamosal of YPM 1828. The inset skull graphics indicate the approximate area of each photograph with a gray box. (Credit: Farke AA, Wolff EDS, Tanke DH, doi:10.1371/journal.pone.0004252.g002) (Click image to enlarge) |
January 28, 2009 — How did the dinosaur
Triceratops use its three horns? A new study led by Andrew Farke,
curator at the Raymond M. Alf Museum of Paleontology, located on the
campus of The Webb Schools, shows that the headgear was not just for
looks. Battle scars on the skulls of Triceratops preserve rare evidence
of Cretaceous-era combat.
"Paleontologists have debated the function of the bizarre skulls of
horned dinosaurs for years now," said Farke. "Some speculated that the
horns were for showing off to other dinosaurs, and others thought that
the horns had to have been used in combat against other horned
dinosaurs. Unfortunately, we can’t just go and watch a Triceratops in
the wild."
If Triceratops fought each other with their horns, wounds from this
combat would be preserved in the fossil bones. So, Farke joined forces
with paleontologists Ewan Wolff of the School of Veterinary Medicine at
the University of Wisconsin and Darren Tanke of the Royal Tyrrell
Museum of Paleontology in order to search museum collections throughout
North America for evidence of these injuries. The researchers focused
on the skulls of Triceratops and a closely-related dinosaur,
Centrosaurus.
"If Triceratops and Centrosaurus only used their horns and frills
for showing off, we would expect no difference in the rate of injury
for both animals," stated Farke. Instead, the team found that the
squamosal bone, which forms part of the frill, was injured 10 times
more frequently in Triceratops than in Centrosaurus. He added, "The
most likely culprit for all of the wounds on Triceratops frills was the
horns of other Triceratops."
Other paleontologists had also noted abnormalities in the skulls of
horned dinosaurs, but later work found that at least some of these
supposed injuries were caused by random, non-traumatic bone resorption
similar to osteoporosis. Additionally, previous researchers only
focused on a handful of specimens. The new study included over 400
observations, which were analyzed statistically to detect differences
between Centrosaurus and Triceratops.
"In the past individual remains have been used to reconstruct the
story of ancient injuries," said co-author Wolff. He continued, "I
think this research shows the great potential of looking at injury
patterns, even less obvious ones, to provide appropriate conclusions.
The features we studied were very subtle and in many cases had been
overlooked."
"Our findings provide some of the best evidence to date that
Triceratops might have locked horns with each other, wrestling like
modern antelope and deer," said Farke. The researchers speculate that
many of the injuries they observed may have been caused by misplaced
horn thrusts from rival animals. Similar injuries are occasionally seen
in modern horned animals.
The size and shape of the horns varied among different horned
dinosaurs, and the researchers hypothesize that different horn shapes
indicate different kinds of combat. Furthermore, some evidence suggests
that certain species may have evolved different kinds of horns in order
to reduce the risk of traumatic injury.
Still, Farke is quick to caution that horned dinosaurs still might
have used their horns and frills for uses beyond fighting. "I like to
think of the headgear on Triceratops as a Swiss army knife," Farke
said. "They probably used their skulls however they wanted, whether it
was for combat, defense, or display."
Source : Public Library of Science