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Armored dinosaurs called ankylosaurs might have wielded sledgehammer-like tail clubs against one another in conflict, in addition to warding off predators like the Tyrannosaurus rex.
A well-preserved fossil of an ankylosaur, a plant-eating dinosaur that lived 76 million years ago, is changing the way scientists understand the armored dinosaurs and how they used their tail clubs.
A study of the fossil revealed spikes on the dinosaur’s flanks that were broken and healed while the animal was still alive. Researchers believe the injuries were caused when another ankylosaur slammed its tail club into the dinosaur.
The study published Tuesday in the journal Biology Letters.
The ankylosaur sported bony plates in varied sizes and shapes across its body; along the sides of its body, these plates acted like large spikes. Scientists also believe ankylosaurs could have used their weapon-like tails to assert social dominance, establish their territory or even while battling for mates.
An ankylosaur using its tail in combat against one another is similar to how animals like deer and antelope use their antlers and horns to fight one another today.
The fossil is of a member of particular species of ankylosaur otherwise known by its classification name, Zuul crurivastator. If the name sounds familiar, it’s because researchers borrowed the name Zuul from a monster in the 1984 film “Ghostbusters.”
The dinosaur’s full name means “Zuul, the destroyer of shins,” given that the ankylosaur’s tail club is thought to have been the enemy of tyrannosaurs and other predators that walked upright on their hind legs.
These tails measured up to 10 feet (3 meters) long, with rows of sharp spikes along the sides. The tail’s tip was fortified with bony structures, creating a club that could swing with the force of a sledgehammer.
The skull and tail were the first pieces of the fossil to emerge in 2017 from a dig site in northern Montana’s Judith River Formation, and paleontologists labored for years to free the rest of the fossil from 35,000 pounds of sandstone. The fossil was so well preserved that remnants of skin and bony armor across the dinosaur’s back and flanks remain, giving it a very lifelike appearance.
This particular ankylosaur seemed pretty banged up by the end of its life, with spikes near its hips and sides missing tips. After sustaining these injuries, the bone healed into a much more blunt shape.
Due to the location on the body, the researchers don’t believe the injuries were caused by a predator’s attack. Instead, the pattern looks like the result of receiving a forceful slam from another ankylosaur’s tail club.
“I’ve been interested in how ankylosaurs used their tail clubs for years and this is a really exciting new piece of the puzzle,” said lead study author Dr. Victoria Arbour, curator of palaeontology at the Royal British Columbia Museum in Victoria, Canada, in a statement.
“We know that ankylosaurs could use their tail clubs to deliver very strong blows to an opponent, but most people thought they were using their tail clubs to fight predators. Instead, ankylosaurs like Zuul may have been fighting each other.”
Arbour suggested the hypothesis that ankylosaurs might have engaged in their behavior years ago, but fossil evidence of injuries was needed — and ankylosaur fossils are rare.
The exceptional Zuul crurivastator fossil helped to fill that knowledge gap.
“The fact that the skin and armor are preserved in place is like a snapshot of how Zuul looked when he was alive. And the injuries Zuul sustained during its lifetime tell us about how it may have behaved and interacted with other animals in its ancient environment,” said study coauthor Dr. David Evans, Temerty Chair and curator of vertebrate palaeontology at the Royal Ontario Museum in Toronto, in a statement.
The Zuul fossil is currently kept in the Royal Ontario Museum’s vertebrate fossil collection.
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