Triceratops’ massive skulls were built for horn-to-horn grappling. The rhino-like Centrosaurus could withstand stabbing its nose horn up and down. And the parrot-faced Psittacosaurus would have been wise to avoid a fight: Its head was ill-suited to handle blows.
New simulations using 3-D models of the heads of five different horned dinosaurs reveal what forces the skulls could withstand in battle. The results provide insight into how these dinosaurs evolved to use their face-based armory in combat, researchers report September 24 in PeerJ.
Ceratopsians — horned dinosaurs like Triceratops — have been hypothesized to use their imposing headgear as armaments for battling with other members of the species.
Fossilized facial injuries consistent with head-to-head violence have provided physical clues. “We know from many fossils that ceratopsian skulls tended to get banged up a little bit … in very particular spots on the frill or on the cheek,” says Andrew Farke, a paleontologist at Raymond M. Alf Museum of Paleontology in Claremont, California. But little else was known about how ceratopsians actually used their horns in battle.
Studying the biomechanics of the animals’ weaponized skulls could provide information on what movements and forces the dinosaurs evolved to tolerate. Such biomechanics research had previously been done on the bite stresses of theropod dinosaurs like Tyrannosaurus and on the forces felt by the club tails of armored dinosaurs, says vertebrate paleontologist Eric Austin Ames Jr.
Ames and his colleagues at the University of Bristol in England developed digital 3-D models of six skulls across five ceratopsian species spread across the group’s evolutionary tree. They simulated the combat stress experienced across the skull, varying the direction of attack and how the weaponry was used. Higher stresses in the skull meant a greater risk of mechanical failure, Ames says. The dinosaurs are more likely to have evolved to fight in a way that was well-tolerated by the skull’s mechanics.
The team found that early members of the group from about 125 million years ago — like the hornless, husky-sized Psittacosaurus — didn’t have skulls well-suited for combat of any type. The pig-sized Protoceratops had a skull that tolerated ramming fairly well. Larger, later-diverging species like Centrosaurus and the three-horned Triceratops and Spiclypeus appeared adapted to a wider range of combat styles.
Centrosaurus may have been a specialized stabber, lunging its head to jab at opponents. “When we tested [the skull] with vertical forces, it actually handled the stresses really well,” Ames says. “But when we tried side-to-side, it did not perform very well.”In contrast, Triceratops and Spiclypeus had skulls that tolerate the forces generated by interlocking horns and wrestling.
Ames thinks ceratopsians’ horns and frills probably first evolved for social and sexual display, but were soon used for full contact purposes. “Throughout their evolutionary history, their [horns’ traits] started to really explode in diversity and that coincided with different intraspecific combat styles,” he says. “This is something we see in modern herbivores.”
Much like with the antlers and horns of modern deer, buffalo or antelope, these weapons could have easily been turned on predators as well. “These adaptations are kind of like a Swiss Army knife,” Ames says. “They can be used for multiple things.”
The team created its 3-D models from surface scans of fossilized skulls. More detailed models that better simulate the complicated internal structure of these dinosaurs’ immense, bizarre skulls could provide even more insight to this prehistoric fight club, Farke says.