Stegosaurus are often portrayed as lumbering plant eaters. But they were lethal fighters when necessary, according to paleontologists who recently uncovered evidence of a carnivorous Allosaurus who was mortally wounded in combat, 147 million years ago.

The wound β€” in the conical shape of a Stegosaurus tail spike β€” would have required great dexterity to inflict and shows clear signs of having cut short the Allosaurus's life.

"A massive infection ate away a baseball-sized sector of the bone," said Houston Museum of Natural Science paleontologist Robert Bakker at a recent meeting of the Geological Society of America, during his presentation on "Stegosaurian Martial Arts."

Similar wounds are seen in rodeo cowboys or horses when they are gored by longhorns, Bakker said. And since large herbivores β€” like longhorn cattle, rhinos and buffalo β€” today defend themselves with horns, it's reasonable to assume spiky herbivorous dinosaurs did the same.

A big difference is that Stegosaurus wielded their weapon on their tails rather than their heads. Skeletal evidence from fossil Stegosaurs suggests their tails were more dexterous than most dinosaur tails.

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"They have no locking joints, even in the tail," Bakker explained. "Most dinosaur tails get stiffer towards the end." But stegosaurus had massive muscles at the base of the tails, flexibility and fine muscle control all the way to the tail tip. "The joints of a Stegosaur tail look like a monkey's tail. They were built for three-dimensional combat."

In order to deliver the mortal wound to the Allosaurus, a Stegosaurus would have had to sweep its tail under the Allosaurus and twist the tail tip, because normally the spikes point outward and backward. That would have been well within the ability of a Stegosaurus, Bakker said.

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