Ankylosaurs fought each other as much as they fought the T. rex

Zuul shows that ankylosaurs may also have used their tail clubs for social dominance.

Scientists have found new evidence of how armored dinosaurs used their iconic tail clubs. The exceptional Ankylosaurus fossil The roar that curdles the blood it has spikes along its flanks that broke off and healed back while the dinosaur was alive, wounds that scientists believe were caused by another blow. from Zuul massive tail club. This suggests that ankylosaurs had complex behaviour, possibly fighting for social and territorial dominance or even engaging in a “rutting” season for mates.

The research, conducted by scientists from the Royal Ontario Museum (ROM), Royal BC Museum and North Carolina Museum of Natural Sciences, was published Dec. 7 in the journal. Biology cards.

The 76-million-year-old plant-eating dinosaur, part of the Royal Ontario Museum’s vertebrate fossil collection, is named after the fictional monster “Zuul” from the 1984 film. Ghostbusters. Initially, the skull and tail had been freed from the surrounding rock, but the body was still encased in 35,000 pounds of sandstone. After years of work, the body was revealed to retain most of its skin and bony armor across its back and flanks, giving a remarkable insight into what the dinosaur looked like in life.

from Zuul the body was covered with bony plates of various shapes and sizes and those on its sides were particularly large and pointed. Interestingly, the scientists noticed that a series of spikes near the hips on both sides of the body have lost their tips and the bone and corneal sheath have healed into a more blunt form. The pattern of these injuries is more consistent with being the result of some form of ritualized or fair fighting with their tail clubs, and was probably not caused by an attacking predator like a Tyrannosaurus due to where they are in the body

“I’ve been interested in how ankylosaurs used their tail clubs for years and this is a really exciting new piece of the puzzle,” says lead author Dr. Victoria Arbour, Curator of Paleontology at the Royal BC Museum and former NSERC Postdoctoral Fellow at the Royal Ontario Museum. “We know that ankylosaurs could use their tail clubs to hit an opponent really hard, but most people thought they were using their tail clubs to fight off predators. Instead, ankylosaurs like Zuul may have been fighting each other.”

from Zuul the tail is about three meters (10 feet) long with sharp spikes running down its sides. The back half of the tail was stiff and the tip was surrounded by huge bony spikes, creating a formidable hammer-like weapon. The roar that curdles the blood means ‘Zuul the Shingle Destroyer’, a nod to the idea that the tail clubs were used to crush the legs of bipedal tyrannosaurs. The new research doesn’t disprove the idea that clubtails could be used in self-defense against predators, but it does show that clubtails would have also worked for combat within species, a factor that likely drove their evolution. Today, specialized animal weapons such as deer antlers or antelope horns have generally evolved to be used primarily to fight members of the same species during battles for mates or territory.

Years ago, Arbor had raised the idea that ankylosaurs might have hit each other in the flanks, and that broken and healed ribs might provide evidence to support that idea. But ankylosaur skeletons are extremely rare, making it difficult to test this hypothesis. Back and tail completely preserved Zuulincluding the skin, allowed an unusual insight into the lives of these incredible armored dinosaurs.

“The fact that the skin and armor are preserved in place is like a snapshot of how Zuul watched when he was alive. And the wounds Zuul sustained during its lifetime tell us how it behaved and interacted with other animals in its ancient environment,” said Dr. David Evans, Temerty Chair and Curator of Vertebrate Paleontology at the Royal Ontario Museum.

The remarkable skeleton of Zuul was found in the Judith River Formation in northern Montana and was acquired by the ROM through the generous support of the Louise Hawley Stone Charitable Trust.

Reference: “Paleopathological evidence for intraspecific combat in ankylosaurid dinosaurs” by Victoria M. Arbour, Lindsay E. Zanno, and David C. Evans, 7 Dec 2022, Biology cards.
DOI: 10.1098/rsbl.2022.0404

Funding for this project was also provided by the Natural Sciences and Engineering Research Council, L’Oreal-UNESCO for Women in Science, Alberta Innovates and the Dinosaur Research Institute.