Forget about dogs: Dinosaurs wagged their tails too

Dogs wag their tails when they are happy, but dinosaurs wagged their tails when they walked, according to new simulations.

Researchers from the Queensland Museum and colleagues created simulations to show how a Coelophysis – a 210-million-year-old theropod, weighing around 15 kilograms – would walk.

Computer simulation of extinct theropod dinosaur Coelophysis running at maximum speed. Grey tiles = 50 cm, played at 0.2× actual speed. Credit: Peter Bishop.

“Essentially, our findings show that dinosaurs like tyrannosaurus and velociraptor wagged their tails from side to side when they ran, which helped them stay balanced,” says Peter Bishop from the Queensland Museum.

“When I first saw the simulation results, I was very surprised, but after running a range of further simulations making the tails heavier, lighter and even no tail at all, we were able to conclusively demonstrate that the tail wagging was a means of controlling angular momentum throughout their gait.”

Read more: How fast was a T. rex?

Angular momentum is the same physics that dictates how ballet dancers and figure skaters perform pirouettes.

The research team included palaeontologists, biochemists and engineers to make the simulations as accurate as possible.

“These cutting-edge, three-dimensional simulations show that we’ve still got much to learn about dinosaurs,” says co-author John Hutchinson of the Royal Veterinary College, UK.

“Our results raise interesting questions about how dinosaur tails were used in a whole array of behaviours, not just including locomotion, and how these functions evolved.”

The study was published in Science Advances.

Computer simulation of extinct theropod Coelophysis running at maximum speed, shown from behind to exemplify tail lateral flexion (wagging). Grey tiles = 50 cm, played at 0.2× actual speed. Credit: Peter Bishop.

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