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Computer simulations reveal dinosaurs
wagged their tails when running
cientists from the RVC using two hind legs to move. This and no tail at all, we were able to
discovered that dinosaurs, like included the modelling of a small demonstrate that tail wagging was a
Tyrannosaurus and Velociraptor, carnivorous dinosaur, Coelophysis, means of controlling angular momentum
Swagged their tails when a 210-million-year-old theropod, throughout gait.”
running, similar to how humans swing weighing around 15kg. To ensure the reliability of their
their arms when moving.
By wagging from side to side, a bipedal approach, the team simulated walking
A team of researchers, led by the RVC, dinosaur’s tail was the main regulator of and running in a modern theropod
have uncovered a surprising functional angular momentum, helping to dynamically dinosaur, a South American tinamou
similarity between dinosaur tails and counterbalance the movement of bird (Eudromia elegans, weighing about
human arms, despite these structures other body parts, like the hindlimbs. 500g). Simulations accurately replicated
being separated by more than 300 Furthermore, when the tail was forced to many important aspects of walking
million years of evolution. The findings wag out of sync with the hindlimbs, the and running, as seen by comparing
reveal that bipedal dinosaurs, like the model’s energy budget greatly increased. the results to previous experimental
Tyrannosaurus and Velociraptor, wagged Just like humans, this ‘control’ of angular data for this species. Leg movement
their tails from side to side when momentum helps to make locomotion patterns, foot–ground forces, centre
running – similar to that of humans more economical and stable. of mass fluctuations and simulated
swinging their arms back and forth Previous studies have always muscle activity patterns all agreed
during movement. This ‘wagging’ was treated non-avian dinosaur tails reasonably well with the experimental
to help angular momentum – a principle as a static, rear extension of the data, bolstering confidence in the
that dictates how ballerinas and figure pelvis, acting as a counterbalance. new methodology.
skaters can execute pirouettes.
However, this research moves beyond Dr John Hutchinson, Professor of
The study, published in Science speculation of the tail’s importance, Evolutionary Biomechanics at the RVC
Advances, was conducted by a team and mechanically demonstrates a and co-author of the study, further
of palaeontologists, biomechanists previously unrecognised, crucial and added: “These cutting-edge three-
and engineers from the UK, Australia, 3D dynamic role. dimensional simulations show that we’ve
Belgium, and the US, and represents Lead author Dr Peter Bishop, former still got much to learn about dinosaurs.
the culmination of over three years’ postdoctoral researcher at the RVC Our results raise interesting questions
work. Using sophisticated computer (currently a research fellow at Harvard about how dinosaur tails were used in
simulations, and leveraging new University, USA), commented: “I was a whole array of behaviours, not just
methods developed by engineers very surprised when I first saw the including locomotion, and how these
working in medicine and aeronautics, simulation results. After running a functions evolved.”
the team assessed running barrage of further simulations, including Previous attempts at dynamic
biomechanics in dinosaurs with tails,
models with heavier tails, lighter tails simulations of dinosaur behaviour
Computer simulations of running locomotion in a modern tinamou bird (brown) and extinct theropod dinosaur Coelophysis (green)
Image credit: Peter Bishop
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