A one-of-a-kind fossil shows that stegosaurs weren't quite the gentle giants some assume them to have been.
The fossil -- of the pubic bone of another Late Jurassic dinosaur known as Allosaurus -- shows clear evidence of a brutal attack by a stegosaur, according to the scientists who have been studying it.
Unearthed in Wyoming in 1999, the fossil seems to confirm the theory among paleontologists that stegosaurs used their spiked tails in combat with other animals.
"This is the only specimen we have where you can see the entry wound for a stegosaur assailant," Dr. Robert Bakker, a paleontologist at the Houston Museum of Natural Science and one of the scientists who discovered the wound, told The Huffington Post. "When animals get chewed up or beat up, you ever hardly have clear evidence… and we have one for this."
(Story continues below.)
The tail spike of a stegosaur seems to have entered the allosaur's pubis from below and passed all the way through. The researchers believe the wound resulted in a lethal infection.
Why are the scientists so sure it was a stegosaur that delivered the wound? Because, they say, the size and shape of the wound match up exactly with the long spikes seen in fossils of stegosaur tails.
Or as Bakker, a self-proclaimed fan of the "Law & Order" TV series, said, "We have more than enough evidence to indict."
Bakker and his colleagues presented their research at the annual meeting of the Geological Society of America in Vancouver, B.C., on October 21, 2014.
Surprised to learn that stegosaurs had a dangerous side? Check out this recent "Talk Nerdy To Me" video for five other big surprises about dinosaurs: