Ankylosaurs, Euoplocephalus, top, with it's relative, Edmontonia, below. Artwork by John Sibbick.

Built like an armored tank, it has been long-thought that ankylosaurs could pack a pretty mean wallop with the end of their tail club. But could an ankylosaur have caused enough damage trying to defend itself against, say, a T. rex? By using CT scans of a Euoplocephalus (a smaller and older relative of the well-known Ankylosaurus), University of Alberta researcher Victoria Arbour has found that a larger tail club could have fractured bone, whereas smaller tail clubs would have produced low-impact forces, but could not fracture bone. The tail club, when swung from side-to-side could have conveniently hit a T. rex’s ankles!

With many dinosaurs to choose from for her research, I asked how Arbour settled on ankylosaurs, and tail clubs in particular.  “When I began my Masters thesis at the University of Alberta I knew I would be working on dinosaurs, but I did not know exactly what I would study for my thesis” says Arbour. “I read many scientific papers and tried to outline gaps in our knowledge of dinosaurs. I've been interested in biomechanics for a while and have been inspired by previous studies using computer modeling and CT scanning to learn more about dinosaurs. My (now) fiancé brought home a kids' dinosaur book from the library he works at, and it had this great picture of an ankylosaur clubbing a Tyrannosaurus, and he asked me if they could actually do that. I said, "I don't know, but I think I might have a thesis project now!"

How did the tail itself resist fracture? “I am still not sure exactly how the tail resists fracture, but I think it might have to do with the shape of the top part of the vertebrae, called the neural arch, in the handle. The neural arch interlocks in Ankylosaurid tails and this might help stiffen the tail and prevent it from breaking” says Arbour.

“Working on tail clubs has been a great experience because I get to work on one of my favorite groups of dinosaurs, use math and physics to answer questions about anatomy and behavior, and I get to play with cool computer programs to do the 3D modeling” she says. Next for Arbour will be looking at the relationships between different Ankylosaurids, to make a family tree of the group.
—Angela Botzer

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