12 June 2007

Tyrannosaurus had poor turning circle

By
Cosmos Online
Turns out T.rex was no ballerina, but was a plodding giant with a turning speed equivalent to a fully laden bus, according to a new study.
Tyrannosaurus had poor turning circle

An automated Tyrannosaurus rex during the world preview of the Walking With Dinosaurs - The Live Experience show in Sydney, January 2007. Experts are continually reviewing the picture we have of the dinosaur as they gather more evidence. Credit: AFP

SYDNEY: Turns out T.rex was no ballerina, but was a plodding giant with a turning speed equivalent to a fully laden bus, according to a new study.

As thrilling as it was to watch the species at its fleet-footed best in the 1993 movie Jurassic Park, the reality is “T.rex couldn’t chase down a jeep, and would have a hard time out-manoeuvring a human,” said John Hutchinson, co-author of a new study, and expert on biomechanics at the University of London’s Royal Veterinary College in England.

In 2002 Hutchinson and his team used biomechanic computer models to reveal that the carnivore likely ambled – rather than sprinted – towards its prey.

They now report in an upcoming Journal of Theoretical Biology that T.rex was even heavier than thought, and consequentially found it hard work to turn while moving.

Can’t catch a jeep

To aid in their analysis, Hutchinson and his team designed computer models in 3-D, which take the bare bones of fossil skeletons and add virtual flesh to them. These models were created by studying the musculature and movement of ostriches – the largest living descendant of the dinosaurs and bipedal land speed record holders capable of clocking up speeds of 65 km/h.

Previous estimates weighed an adult Tyrannosaurus in at three to four tonnes with a top running speed of 40 km/h – but with new, more accurate models the researchers argue that the average adult would have weighed as much as six to eight tonnes.

“A really big individual might even have weighed 10 tonnes,” said Hutchinson.

This hefty mass would not have helped with mobility. The huge inertia – or resistance to turning – caused by a heavy head and tail far from the animal’s centre of mass, would have made changing direction difficult.

It would probably have taken one to two seconds for the animal to turn only 45°, said Hutchinson – an amount that humans, being vertically oriented and tail-less, can spin in just fractions of a second.

Fatal flaw

The study “raises the bar on how dinosaur biomechanics should be done,” commented Stephen Gatesy, a biologist from Brown University in Rhode Island, USA. He says the work brings scientists closer to answering big questions, such as whether T.rex was a hunter or a scavenger.

“This strikes me as the most sophisticated analysis of the body mass, body mass distribution, and implications … for the locomotion of T.rex to date,” said Jim Farlow, a geoscientist at Indiana University in Fort Wayne. According to Farlow, the find suggests that large adult T.rex probably didn’t attack smaller, more agile prey – but went for larger, lumbering dinosaurs instead.

Hutchinson concurs, adding that the hefty duck-billed Edmontosauraus or the horned Triceratops would have been more likely to end up as T.rex lunch than small, fast animals.

Although T.rex could potentially manage a leisurely jog, it was better off not trying, since any fall could be potentially fatal. When a creature the size of a Tyrannosaurus topples over, “It hurts itself badly and may even die,” said Farlow.

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