- Tyrannosaurus probably couldn't run. The dinosaur would
have needed unfeasibly large leg muscles to generate enough power to
sprint,
researchers now calculate.
-
- Those planning Jurassic Park IV needn't be too depressed.
With its 2.5-metre-long legs, a brisk walk would have carried T. rex along
at over 20 kilometres per hour - enough to catch many other
dinosaurs.
-
- "It could have walked as fast as a running
rhino,"
says palaeontologist Per Christiansen of the University of Copenhagen.
"If you ever need to outrun a Tyrannosaurus, I suggest you do it on
horseback."
-
- Engineers John Hutchinson and Mariano Garcia, of Stanford
University, Palo Alto, California, have estimated the minimum amount of
leg muscle needed for running in different-sized animals. This depends
on leg and muscle-fibre length, and the animal's stance, among other
factors.
-
- "With extinct animals you can't prove
anything,"
says Garcia. "But given what we know about other animals that are
good runners, it's unrealistic that Tyrannosaurus could run."
-
- Researchers have argued over whether T. rex was a hunter
or a scavenger. Its inability to run and its puny forearms hint it could
only handle carrion, suggests Andrew Biewener, who studies animal
locomotion
at Harvard University in Cambridge, Massachusetts.
-
- But this needn't have disqualified Tyrannosaurus from
catching live meat, he says. Its potential prey were other large dinosaurs,
probably much more lumbering than itself.
-
- Solid Muscle
-
- "Things have a harder time moving as they get
bigger,"
explains Garcia; muscle power does not keep pace with body mass. This is
why fleas can jump so much higher than we can, relative to their
size.
-
- An inability to run and puny forearms hint T. rex could
only handle carrion Andrew Biewener, Harvard University,
Massachusetts
-
- In running, both feet leave the ground. A 6,000 kg T.
rex would have needed more than 80% of its total mass in its hind leg
muscles
to achieve this - an implausibly high figure, the duo concludes1. The
maximum
seen in living land vertebrates is about 50%.
-
- A chicken, in contrast, could run with only about 9%
of its mass in its leg muscles, Hutchinson and Garcia estimate. Real
chickens
have 17%. A Tyrannosaurus-sized chicken would need an impossible 99% of
its body mass in each leg to run.
-
- The finding might explain the absence of fossil
footprints
showing a Tyrannosaurus in full flight. Tyrannosaurus' smaller - although
still fearsome - relatives could run at 30 kilometres per hour, as
illustrated
by a trackway recently found in the United Kingdom2.
-
- The threshold dividing dinosaur runners and walkers
probably
lay between a body weight of 1,000 and 2,000 kg, says Biewener.
-
- References
-
- 1. Hutchinson, J. R. & Garcia, M. Tyrannosaurus was
not a fast runner. Nature, 415, 1018 - 1021, (2002).
-
- 2. Day, J. J., Norman, D. B., Upchurch, P. & Powell,
H. P. Dinosaur locomotion from a new trackway. Nature, 415, 494 - 495,
(2002).
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- © Nature News Service / Macmillan Magazines Ltd
2002
-
- http://www.nature.com
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