Digital reconstruction of trix the t-rex

How fast was a T. rex?

Walking speed of a T-rex. Credit: Rick Stikkelorum, Arthur Ulmann & Pasha van Bijlert

The Tyrannosaurus rex may have walked at a leisurely speed of 4.6km/h, according to 3D tail reconstruction.

Researchers from Vrije Universiteit Amsterdam in the Netherlands built a biomechanical model to estimate how much a T. rex’s tail affected its stride.

“The walking speeds found here are lower than earlier estimations for large theropods,” say the authors in their paper, published in The Royal Society Open Science.

The researchers estimated the species by creating a 3D reconstruction based on the dimensions of an adult T. rex specimen called Trix, held in a collection at the Naturalis Biodiversity Center in Leiden, the Netherlands.

Trix the Tyrannosaurus. Credit: Pasha van Bijlert

Animals tend to walk in a way that uses as little energy as possible. This means they capitalise on limbs and body parts beyond just their legs to determine their gait.

For two-legged T. rexes, they probably used their tail muscles when walking. The tail was suspended passively by spring-like ligaments and would sway up and down with each step at a natural frequency, which the researchers were able to estimate from the biomechanical model. Using this frequency, they could then estimate the dinosaur’s walking speed, as for each tail bounce, the dinosaur would take one step.

The end result? The T. rex was a slow walker, with a preferred speed of 4.6km/h (1.28m/s) – about the average speed of a human.

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