Researchers from the Royal Ontario Museum (ROM), the Royal BC Museum, and the North Carolina Museum of Natural Sciences have found new evidence about how armored dinosaurs used their famous tail clubs.

The unique specimen of the ankylosaur Zuul crurivastator features spikes along its flanks that were broken and re-healed while the dinosaur was still alive. The experts believe that these injuries were caused by a hit from the huge tail club of another Zuul.

This shows that ankylosaurs had sophisticated behavior, maybe participating in conflicts over social and territorial dominance or even having mating seasons. The findings of the study were presented in a paper that was published in the journal Biology Letters.

The dinosaur, which lived 76 million years ago and ate plants, is part of the Royal Ontario Museum’s collection of vertebrate fossils. It was named after the monster “Zuul” from the 1984 movie “Ghostbusters.”

At first, the head and tail were freed from the rock around them, but the rest of the body was still covered in 35,000 pounds of sandstone.

After years of work, it was found that most of the skin and bone armor on the dinosaur’s back and sides were still there. This gave a very clear picture of what the dinosaur looked like when it was alive.

The bony plates down Zuul’s flanks were very big and spikey, although they were present all over the creature.

Scientists found it interesting that some of the spikes near the hips on both sides of the body are missing their tips, and the bone and horny sheath have grown back into a more blunt shape.

Because of where these injuries are on the body, it’s more likely that they were caused by ritualized fighting or jousting with their tail clubs than by an attack by a predator like a tyrannosaur.

“I’ve been interested in how ankylosaurs used their tail clubs for years and this is a really exciting new piece of the puzzle,” adds lead author Dr. Victoria Arbour. “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.”

The length of Zuul’s tail is around two meters (10 feet), and its sides are covered with jagged spikes. The tail was a fearsome sledgehammer-like weapon, with the tip covered with enormous bony lumps and the rear half rigid.

Zuul crurivastator means “Zuul, the destroyer of shins.”

This name comes from the idea that bipedal tyrannosaurs’ legs were broken by tail clubs.

However, it demonstrates that tail clubs would have also been useful for intra-species conflict, which is what most likely drove their development. The new study does not disprove the hypothesis that tail clubs might be employed in self-defence against predators.

Specialized animal weapons like a deer’s antlers or an antelope’s horns are mostly used to fight other members of the same species when they are fighting for mates or territory.

Years ago, Arbour suggested that ankylosaurs may have hit each other in the flanks, and he thought that broken and healed ribs could be proof that this happened.

But because ankylosaur remains are so uncommon, it is difficult to evaluate this theory. It was possible to have a rare look into the life of these amazing armored dinosaurs because of Zuul’s back and tail, which were totally preserved, including the skin.

“The fact that the skin and armour are preserved in place is like a snapshot of how Zuul looked when it 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,” adds Dr. David Evans.

The remarkable Zuul skeleton was found in the Judith River Formation in northern Montana. 

Source: 10.1098/rsbl.2022.0404

Image Credit: © Royal Ontario Museum


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