Some Dinosaurs May Have Wagged their Tails to Help Them Run

www.scientificamerican.com
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This may be for the same reason humans swing their arms when walking and running.
Small-armed, two-legged dinosaurs may have wagged their tails to help them run, for the same reason humans swing their arms, according to a new study.

Figuring out how extinct species moved about in the world is not easy, as just bones and footprints are left to analyze. Most previous studies on bipedal dinosaurs — those that stand on two feet, such as Tyrannosaurus rex — have deduced movement by focusing on the animals' legs.

Scientists had assumed the big tails of bipedal dinosaurs were passive structures to help with balance, said lead author Peter Bishop, a postdoctoral fellow at Harvard University (who, during the majority of the study, was at the Royal Veterinary College in Hatfield in the U.K.).

In the new study, Bishop and his colleagues modified a simulation method used in the fields of medicine and aerospace to probe deeper into the biomechanics of bipedal dinosaurs.

First, they tested their simulations on a living creature, a Tinamou bird — an order of ground-dwelling birds found in Central and South America that have similar characteristics to ancient bipedal dinosaurs. They then made sure that the results of their simulations matched real-life observations.

Then, the researchers tested their simulation on a single species of bipedal dinosaur. Coelophysis bauri; a fast, long-limbed species that lived during the Triassic period, which spanned from 251.9 million to 201.3 million years ago. They fed the computer simulation a digital model of the animal, taken from CT scans of its fossil bones.

With the computer simulation, the researchers could divide the dinosaur's backbone into multiple segments, such as the body, head, neck, back and tail. The researchers were then able to…
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