Complex armored dinosaur behavior: Ankylosaurs fought as much as they fought T. rex

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

Scientists have found new evidence of how armored dinosaurs used their signature tail clubs. The exceptional fossil of the ankylosaurus The bloodcurdling roar has spikes along its flanks that were broken off and healed while the dinosaur was alive – injuries that scientists believe were caused by a strike by another at Zuul massive tail club. This suggests that ankylosaurs exhibited complex behavior, possibly vying for social and territorial dominance or even engaging in a “rut” season for mates.

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

The 76-million-year-old herbivorous dinosaur, part of the Royal Ontario Museum’s Vertebrate Fossil Collection, is named after the fictional monster ‘Zuul’ from the 1984 film ghost hunters. 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, it was revealed that the body retained most of the skin and bone armor all over its back and flanks, giving a remarkable view of what the dinosaur looked like in life.

at Zuul the body was covered with bony plates of various shapes and sizes and those along its sides were particularly large and pointed. Interestingly, the scientists noticed that a number of spikes near the hips on both sides of the body were missing their ends, and the bone and horny sheath had healed into a more blunt shape. The pattern of these injuries is more consistent with the result of some form of ritualized combat or jousting with their tail clubs, and was probably not caused by an attacking predator like a tyrannosaur due to where they are on 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 clubs to deliver very powerful blows to an opponent, but most people thought they used their clubs to fight off predators. Instead, ankylosaurs like Zuul may have fought.

at Zuul the tail is about three meters (10 feet) long with sharp spikes along its sides. The rear half of the tail was stiff, and the tip was encased in huge bony patches, creating a formidable hammer-like weapon. The bloodcurdling roar stands for “Zuul, the Shin-Smasher”, a nod to the idea that clubs were used to break the legs of bipedal tyrannosaurs. The new research does not refute the idea that tail clubs could be used in self-defense against predators, but shows that tail clubs would also have functioned for combat within species, a factor that likely drove their evolution. . Today, specialized animal weapons like deer antlers or antelope horns have generally evolved to be used primarily to fight members of the same species in battles for mates or territory.

Years ago, Arbor put forward the idea that ankylosaurs may have bumped into each other in the flanks, and that broken and scarred ribs might provide evidence to support that idea. But ankylosaur skeletons are extremely rare, making it difficult to verify this hypothesis. The fully preserved back and tail of Zuulincluding skin, allowed an unusual glimpse into the life of these incredible armored dinosaurs.

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

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

Reference: “Paleopathologic Evidence for Intraspecific Combat in Ankylosaurid Dinosaurs” by Victoria M. Arbour, Lindsay E. Zanno, and David C. Evans, December 7, 2022, Biology Letters.
DOI: 10.1098/rsbl.2022.0404

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