This fossil pair, an armored stegosaurus (left) and allosaurus (right) were discovered locked in combat in a Wyoming quarry, with the allosaurus jaw clenched around one stegosaurus foot.
The hunting allosaurus used its head like a baseball bat, knocking its prey sideways before using its teeth to tear away flesh.
Allosaurs, which were built like tyrannosaurs only smaller, lived and dined in North American, Europe and Asia in the late Jurassic period, about 150 million years ago.
"Allosaur would strike sideways like a crocodile and pull straight back," Eric Snively, a biomechanics researcher at Ohio University, told NBC News. The dinosaur bit into its prey with teeth as sharp as knife blades, and then tugged the flesh away with upward strokes — just like a falcon does today. The big difference is that Allosaurus stood 15 feet (4.5 meters) tall.
With a skull full of cavities, allosaurs were airheads. But those air pockets made for a lighter nut and a faster, more powerful head-butt. Snively and his colleagues believe it was swung effectively, like a baseball bat held by its thick end. The team explains their findings in Paleontologia Electronica.
Snively and a team at Ohio University made CT scans of the cast of an allosaur fossil called Big Al, and filled in tissue patterns using modeling software. Then they simulated the movements of the dinosaur's neck and head. "The head and neck were precision instruments," Snively said. "Despite being moderately long and nasty-looking, it was wielded like a surgeon wielding a scalpel."
The dino's larger cousin, Tyrannosaurus rex, lacked some of that grace. "T. rex was like a gorilla with an ice pick," Snively said. The larger carnivore would bite into its prey and thrash it around like a crocodile.
Tooth marks found on fossilized bones suggest that allosaurs feasted on giant long-necked dinosaurs, and there's also evidence that they also dined on stegosaurs. Some of the creatures that allosaurs ate were dead already — since most predators scavenge when they can, Snively says — but at least some of its prey would have been eaten alive.
Witmer Lab / Ohio U.
This illustration shows the skeleton and soft tissues of an allosaur's head and neck.
More about dinosaurs at dinner time:
- How dinosaurs chewed
- Buuurp! Methane-emitting dinosaurs could have warmed the earth
- 'Lonely' meat-eating dinosaur from Madagascar helps fill in fossil gap
Along with Eric Snively, John Cotton, Ryan Ridgely, and Lawrence Witmer also contributed to "Multibody Dynamics Model of Head and Neck Function in Allosaurus," the study published by Paleontologica Electronica.