New research suggests that the tails of giant armored dinosaurs known as ankylosaurs may have evolved to strike each other rather than deter hungry predators. This is a complete change from what was previously believed.
Before the paper published today in Biology Letters, most scientists viewed the dinosaur’s tail, a substantial bony protrusion consisting of two oval-shaped knobs, primarily as a defense against predation. The team behind the new paper claims that this is not necessarily the case. To make their case, they focused on years of ankylosaur research, analysis of the fossil record, and data from an exceptionally well-preserved specimen. Zuul crurivastator🇧🇷
Zuul’s name actually encapsulates the previous idea. “Zuul” originally refers to a creature Ghostbustersare two Latin words that make up its species name raw (shin or shin) and Vastator (destroyer). Hence the shin-destroyer: a direct reference to where the dinosaur’s club struck an approaching tyrannosaur or other theropod.
However, this name was given when only the skull and tail were excavated from the rock in which the fossil was enclosed. After years of skillful work by fossil preparers at the Royal Ontario Museum, Zuul’s entire back and flanks have been exposed, providing important clues as to what its tail club would have aimed at.
Lead authorDr. Victoria Arbor is currently Curator of Paleontology at the Royal British Columbia Museum, but she is a former NSERC postdoctoral fellow at the Royal Ontario Museum in Toronto. It has been Zuul’s home since 2016, two years after its first discovery in Montana. He spent years studying ankylosaurs, a type of dinosaur, that appeared in the fossil record from the Jurassic to the end of the Cretaceous period. Some species of ankylosaurs have tail clubs, while others nodosaurs do not. This difference raises some questions about what these structures are used for.
“I think the natural answer is, ‘Can they use their tails as weapons?’ “Who are they using that weapon against?” Arbor explained. “So I really started thinking about it.
In 2009, he a paper This suggested that ankylosaurs may have used their tail clubs for intraspecific combat—fights with other ankylosaurs. This work focused on the potential impact of tail clubs when used as weapons, particularly as clubs come in a variety of shapes and sizes and in some species are not even present until the animal reaches adulthood. By measuring extant fossil tail clubs and estimating the force of the blows they could have delivered, he found that the smaller clubs (about 200 millimeters, or half a foot) were too small to be used as a defense against predators.
He recommended further research, noting that if ankylosaurs were using them for intraspecific combat, one might expect to see injuries along the flanks of adults because ankylosaurs could only swing their tails so far.
It’s one thing to have an idea of an extinct animal, it’s another to have proof. Ankylosaur fossils are generally rare; Dinosaurs are rarer, with the preservation of tissues that would be damaged in these battles. So it’s amazing that Arbor can test his ideas thanks to an animal with its entire back – most of its skin and all – intact.
“I came up with the idea that we would expect to see damage on the flanks, just based on how they might line up against each other,” Arbor told Ars. “And then ten years and a little later, we wound up this amazing skeleton of Zuul where we thought we’d see it. And it was pretty exciting!”
The back and flanks of the Zuul are covered with various spikes and bony structures called osteoderms. As Arbor predicted, there is evidence of broken and damaged osteoderms on both sides of the flanks, some of which appear to have healed.
“We also did some kind of basic statistics to show that injuries are not randomly distributed throughout the body,” he said. “They’re really only limited to the sides in the area around the hips. This cannot be explained by random coincidences. It seems so [the result of] repetitive behavior.”
There are only a few well-preserved ankylosaurs, including at least one nodosaur. Borealopelta At the Royal Tyrrell Museum. The authors note that no known nodosaurs with a German point lack comparable injuries. As mentioned earlier, nodosaurs do not have tail clubs and therefore could not use them against each other.
Equally important, the damage is not accompanied by evidence of predation. There are no bite marks, puncture wounds, or teeth scratches anywhere on Zuul’s body.
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