T. Rex were lumbering dinos much like today’s elephants

The Tyrannosaurus rex was no agile dinosaur and would have just plodded along like an elephant, according to a new study that estimated the "speed limit" of nerve signals running through the mighty reptile's body.

When a vertebrate - an animal with a backbone - stubs its toe, electrical signals are transmitted from the toe to the spinal cord by a nerve, which comprises bundles of long, fibrelike cells.

Since the scientists couldn't examine a T. rex's nerves directly, they analysed how nerves work in a range of modern animals, from the tiny shrew to midsize dogs and pigs to massive Asian elephants.

The research group discovered that, for all body sizes, nerves have a basic speed limit of about 180 feet a second. That's the fastest a signal can travel from an animal's feet to its spinal cord - the kind of signal that's necessary for walking and running.

At that speed limit, big animals like elephants can't run too fast or they're effectively running blind.

Suppose an elephant steps on a pebble while it is running fast, "its foot would be nearly off the ground before it could do something in response to that troublesome pebble," said study leader Max Donelan of Simon Fraser University in Burnaby, Canada.

The same follows for T. rex, according to study co-author John Hutchinson, an expert on dinosaur movement at the Royal Veterinary College in London.

"Nerves are nerves-in vertebrates anyway. So the principles will apply generally to dinosaurs, too," The National Geographic quoted, Hutchinson, as saying.

The research says there's a trade-off between the number of nerve cells in a bundle and how fast the nerve can transmit a signal.

For a big animal like an elephant to be as fast as a shrew and still feel every step, the elephant's nerves would have to be 100 feet thick, which is impossible.

Instead, elephant nerves can either be relatively slow and sensitive or fast and dulled.

As long as a bus and weighing nearly 6.5 tons, the average T. rex would also have needed to move slowly to feel with its feet, the study suggests.

The idea that T. rex lumbered like an elephant fits with other studies of the dinosaur's body, including one paper that found that T. rex's leg muscles would have to have been heftier than its whole body weight for the dinosaur to have been a speed demon."To be agile, Tyrannosaurus would need to be both all muscle and all nerve," Donelan said.

Nevertheless, elephants can occasionally get up to a fast clip, sometimes charging fast enough to catch people. The same goes for big dinosaurs, the Royal Veterinary College's Hutchinson said.

According to the researchers, Tyrannosaurus rex were "by no means slow, sluggish, ponderous, clumsy animals. They still would have been impressive and exciting to see, and capable of surprising feats from time to time."

The study appears in the Proceedings of the Royal Society B.