Computer simulations of dinosaurs has yielded an accidental discovery, their tails wagged when they walked.
Historically it has been accepted that the giant creatures' tails were a counterbalance, helping to keep them steady.
Studying locomotion in fossils has always been tricky, but a research team at the Royal Veterinary College in London has found dinosaurs' tails actually moved and helped them to walk and run more efficiently.
Dr Peter Bishop, who is currently a research fellow at Harvard University, says high tech simulations have revealed their tails could actually swing up and down
Photo: Peter Bishop
The wagging was systematic, not random, Bishop told Kathryn Ryan.
“It's not just a random, left right flick here and there. It's a very systematic, organised, orchestrated movement of the tail in step with the hind legs.
“For bipedal animal like the T Rex if the leg left leg retracts backwards, then the tail swings to the left, and then as the right leg retracts backwards, the tail swings to the right.”
The study looked at the Coelophysis, a three-metre long wolf-sized dinosaur.
Previous studies had assumed the tail was there for balance, he says.
“We'd always just assumed that the tail didn't really do much, they just kind of stuck out the end as a more or less static counterbalance to balance the front half of the animals.
“So these bipedal animals could stay on two legs. And we really didn't give much thought or much attention to what the tail could have been doing on its own beyond just being a counterbalance.”
But when they ran simulations a different picture emerged.
“It became apparent this tail is not just doing a little bit of random movement here and there, it's actually doing a very systematic, very regular pattern. And it's not just doing it a little bit, it's quite significant.”
They believe the tail served a similar purpose to that of arms in humans, he says.
“The fact we humans swing our arms is really just about trying to achieve the same biomechanical effect, but using what anatomy we have available at our disposal.
“We don't have a long tail, we don't have a tail at all. But we have long arms long and heavy arms. And so, we swing those in phase, in lockstep with our legs to regulate what we call angular momentum.”
By contrast dinosaurs had tiny arms, he says.
“We hypothesize the tail is functionally achieving the same outcome in dinosaurs as the swinging arms of us humans.”
The fossils revealed mush about how dinosaurs moved, he says.
“We only have really the static, the dead, dusty fossil bones of these extinct animals like dinosaurs. But by studying the structure of the bones in terms of the shapes of the ends of the bones, and how they articulated with one another at the joints, like the hip joint, the knee joint, the ankle joint, and also by studying the tell-tale signatures that muscles leave on the bones, what we call muscle scars.
“Even though the muscles aren't preserved anymore, they've long rotted away, where they attach to the bones is quite visible in terms of the structure of the bones themselves.
“By putting all this evidence together, we can build up a digital musculoskeletal model that mathematically encodes how the bones articulate, how the muscles attach from one vein to the next, how the contraction of the muscles produces force that moves the bones and rotates the joints.”
The simulation then calculates how it would move to achieve an optimal outcome, he says.
“When we do all of that, we ultimately end up with these digital simulations, these animations of animals, doesn't have to be a dinosaur can be any animal, of these animals moving through space.”
Their simulations found the Coelophysis could run at about six and a half meters per second.
“It's only by using these kinds of simulations of walking, or running or jumping or whatever, that it will allow us to better appreciate dinosaur diversity and in all of its splendour.”
