The tank-like armored dinosaurs could have punched each other — and not just predators — with giant knuckles attached to the end of their tails. Thanks to new fossil discoveries, researchers have a clearer picture of how these rugged herbivores used their vile weapons.
Many of the dinosaurs known as ankylosaurids had a heavy, possibly microwave-sized tail rod. Scientists and artists have long thought of the natural sledgehammer as a defensive weapon against predators, says paleontologist Victoria Arbour of the Royal British Columbia Museum in Victoria, Canada.
Fossil evidence of the tail club target was largely lacking until Arbor and her colleagues cut more rock from the same skeleton they used to describe a new armored dinosaur, Zuul crurivastator2017 (SN: 6/12/17).
There are five broken spikes on the sides of the dinosaur. The team’s statistical analysis revealed that damaged spikes clustered in specific areas of the body. If large carnivorous dinosaurs had inflicted these injuries, they would have likely been distributed more randomly, including bite and scratch marks, Arbour said.
Instead, the damage is more in line with clubbingthe researchers reported on December 7 at Biology Letters.
Armored dinosaurs started out with either no or too small tail bars for primary defense, and they grew proportionally larger as they aged. Similar growth patterns appear in some modern animal weapons, such as deer antlers. Tank-like dinosaurs likely fought with each other over mates, food, or territory, as stags and giraffes do today.
That tail is also useful in a pinch. “Wagging the tail at the ankle of a two-legged predator is a very effective weapon,” Arbour said.
“Ankylosaurus is often portrayed as a dumb, lonely dinosaur,” she added. The findings “suggest that their behavior may be more complex than we thought.”