Ankylosaurs used their sledgehammer tails to fight each other

Ankylosaurs used their sledgehammer tails to fight each other
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Armored dinosaurs called ankylosaurs may have used sledgehammer-like tail clubs against each other in conflict, in addition to repelling predators like the Tyrannosaurus rex.

A well-preserved fossil of an ankylosaur, a herbivorous dinosaur that lived 76 million years ago, is changing the way scientists understand armored dinosaurs and how they used their tail clubs.

Examination of the fossil revealed spines on the dinosaur’s flanks, which were broken and healed while the animal was still alive. Researchers believe the injuries were caused when another ankylosaur rammed its tail club into the dinosaur.

The study was published in the journal on Tuesday biology letters.

The ankylosaur wore bony plates of various sizes and shapes across its body; On the sides of his body, these plates acted like large spikes. Scientists also believe that ankylosaurs may have used their weapon-like tails to assert social dominance, establish their territory, or even compete for mates.

An ankylosaur using its tail to fight one another is similar to how animals like deer and antelope use their antlers and horns to fight one another today.

The fossil belongs to a specific species of ankylosaurs otherwise known by its classification name. Zuul Crurivastator. If the name sounds familiar, that’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,” since the ankylosaurid’s tail club is believed to have been the enemy of tyrannosaurs and other predators that walked upright on their hind legs.

The ankylosaur's skull was one of the first parts of the fossil to be recovered.

These tails were up to 3 meters long and had rows of sharp spikes on their sides. The tip of the tail was reinforced with bony structures, creating a club that could swing with the force of a sledgehammer.

The skull and tail were the first parts of the fossil to emerge from a 2017 dig in the Judith River Formation in northern Montana, and paleontologists worked for years to extricate the rest of the fossil from 35,000 pounds of sandstone. The fossil was so well preserved that remnants of skin and bony carapace remain on the dinosaur’s back and flanks, giving it a very lifelike appearance.

This particular ankylosaur seemed pretty battered by the end of its life, with spikes near its hips and sides missing tips. After suffering these injuries, the bone healed to a much blunt form.

Because of the location on the body, researchers don’t think the injuries were caused by a predator attack. Instead, the pattern looks like the result of a powerful smack from another ankylosaur’s tail club.

An injured spine can be seen on the right side of the fossil, which has healed over time.

“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 study lead author Dr. Victoria Arbor, curator of paleontology at the Royal British Columbia Museum in Victoria, Canada, in a statement.

“We know that ankylosaurs could use their tail clubs to deliver very powerful blows to an opponent, but most people thought they used their tail clubs to fight off predators. Instead, ankylosaurs like Zuul could have fought each other.”

Arbor proposed the hypothesis that ankylosaurs may have committed their behavior years ago, but fossil evidence of injury was needed — and ankylosaur fossils are rare.

The fossil contains the dinosaur's head, body and tail.

The extraordinary Zuul Crivastator fossil helped fill this knowledge gap.

“The fact that the skin and armor are in place is like a snapshot of what Zuul looked like when he was alive. And the injuries Zuul sustained during its lifetime tell us how it may have behaved and interacted with other animals in its ancient environment,” said study co-author Dr. David Evans, Temerty Chair and Curator of Vertebrate Paleontology at the Royal Ontario Museum in Toronto, in a statement.

The Zuul fossil is currently preserved in the Royal Ontario Museum’s Vertebrate Fossil Collection.

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