T. Rex Plodded Like an Elephant, Nerve Study Says

The mightyTyrannosaurus rexwas no quick, agile killing machine—the"tyrant king"dinosaur just didn't have the nerves.

Instead, most timesT. rexprobably plodded along like an elephant, according to a new study that estimated the"speed limit"of nerve signals running through the dinosaur's body.

(Related:"T. RexWas Slow-Turning Plodder, Study Suggests.")

When a vertebrate—an animal with a backbone—stubs its toe, electrical signals get carried from the toe to the spinal cord by a nerve, which is made up of bundles of long, fiberlike cells.

Since the researchers couldn't study aT. rex's nerves directly, the team looked at how nerves work in a range of modern animals, from the tiny shrew to midsize dogs and pigs to massiveAsian elephants.

(Related:"'Dinosaur Mummy' Found; Has Intact Skin, Tissue.")

The scientists found that, for all body sizes, nerves have a basic speed limit of about 180 feet (55 meters) 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 essential for walking and running.

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

Suppose an elephant steps on a pebble, said study leaderMax Donelanof Simon Fraser University in Burnaby, Canada. If the pachyderm was running fast,"its foot would be nearly off the ground before it could do something in response to that troublesome pebble."

The same goes forT. rex,said study co-authorJohn Hutchinson, an expert on dinosaur movement at the Royal Veterinary College in London.

"Nerves are nerves—in vertebrates anyway,"Hutchinson said."So the principles will apply generally to dinosaurs, too."

T. rexWould Still Have Been Impressive, Exciting

According to the study, 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 such as an elephant to be as fast as a shrew and still feel every step, the elephant's nerves would have to be 100 feet (30 meters) thick—clearly impossible.

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

As long as a bus and weighing around 6.5 tons, the averageT. rexwould also have needed to move slowly to feel with its feet, according to the study, which appears Wednesday in theProceedings of the Royal Society B.

The idea thatT. rexlumbered like an elephant fits with other studies of the dinosaur's body, including one paper that found thatT. 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,Tyrannosauruswould need to be both all muscle and all nerve,"Simon Fraser's Donelan said.

(Related:"'Mighty'T. RexMostly Picked Off Youngsters?")

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

Tyrannosaurus rexwere"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."

forNational Geographic News

Source