The dinosaurs that fought with clubs

by time news

With six meters in length, about 2,500 kilos in weight and a shell full of spines, the exceptional ankylosaur The blood-curdling roar it could easily be compared to an armored tank. Released in 2017, the first part of its name refers to the goalkeeper from the movie ‘Ghostbusters’ (1984) -the monster that possesses Sigourney Weaver-, while the second, which means ‘pimples destroyer’, alludes to its ability to use its powerful rigid tail, ending in a bony protrusion, as if it were a colossal club.

For a long time, it was thought that the tail served these dinosaurs to protect themselves from attacks by tyrannosaurs and other predators. However, based on the fossil of a specimen in which curious lesions can be seen, a team of researchers has come to the conclusion that the clubbing was shared between them. As explained in a study published in ‘Biology Letters’, Zuul used the tail to fight for social dominance, territory or to compete during the mating seasonas modern deer do with their antlers.

The Zuul fossil, a herbivorous dinosaur that lived 76 million years ago, is part of the collection of the Royal Ontario Museum (Canada). Initially, the skull and tail had been freed from the surrounding rock in northern Montana, USA, but the body was still encased in 16,000 kilograms of sandstone. After years of work, it was revealed that the body had retained most of the skin and bone armor across its entire back and flanks, providing a remarkable picture of what the dinosaur might have looked like in life. The body was covered with bony plates of different shapes and sizes. The ones on the sides were particularly large and pointy.

The scientists noted that several spikes near the hips on both sides of the body were missing their tips and that the bone and horn sheath healed into a more blunt shape while the dinosaur was alive. Due to their location on the body, these lesions did not correspond to those that would be produced by an attack by a predator such as a tyrannosaurus. However, they seemed more consistent with the result of some kind of ritualized combat, a tail-fight with another ankylosaur.

“For years I was interested in how ankylosaurs used their tails and this is a really exciting new piece of the puzzle,” says lead author Victoria Arbor, curator of paleontology at the Royal British Columbia Museum (Victoria, Canada). “We know that ankylosaurs could use their tails to deliver very powerful blows to an opponent, but most people thought they did it to fight off predators. Instead, ankylosaurs like Zuul may have been fighting each other,” she argues.

like a mallet

Zuul’s tail is about three meters long with sharp spikes along its sides. The rear half of the tail was rigid and the tip was encased in huge bony protrusions, creating a formidable mallet-like weapon.

The new research doesn’t refute the idea that the tail could be used in self-defense against predators, but it does show that it would have worked for intraspecies combat as well, a factor that probably fueled its evolution. Today, specialized animal weapons, such as deer antlers or antelope horns, have evolved to be used primarily to fight members of the same species during tag or territory battles.

Years ago, Arbor had put forward the idea that ankylosaurs might have hit each other on the flanks, and that healed and broken ribs might support this idea. But ankylosaur skeletons are extremely rare, making it difficult to test this hypothesis. Zuul’s fully preserved back and tail, including skin, allowed for an unusual glimpse into the lives of these incredible armored dinosaurs.

“The fact that the skin and armor are kept in place is like a snapshot of what Zuul looked like when he was alive. And the injuries Zuul sustained during his lifetime tell us how he may have behaved and interacted with other animals in his ancient environment,” explains David Evans, curator of vertebrate paleontology at the Royal Ontario Museum.

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