November 14, 2011

Science Illuminated: Run, T. Rex, run!

Tyrannosaurs may have been faster than previously thought... or slower, depending on who you ask.

Dinosaur paleontologists seem to love arguing over how fast Tyrannosaurs could run. 

In the 70's, R. McNeill Alexander came up with a formula to estimate speeds by measuring the size and spacing of fossilized footprints. Alexander acknowledged its limitations: he made the formula by observing living mammals (like horses). Tyrannosaurs probably didn't run the same way a horse runs. Alexander's formula gives a rough estimate for Tyrannosaurs' speed at around 9 miles per hour (MPH).

You can also look at bones to figure out how an animal moved and how fast it could run. This is called biomechanics. It's a bit like looking at car parts and figuring out how they work together.

A comparison of running speeds (cc Wikimedia)

A 2007 paper by University of Manchester scientists used biomechanics to clock Tyrannosaurs at around 18 MPH max.**

A new paper suggests that Tyrannosaurs may have "power walked" faster by using their large butt muscles to power short, fast strides.*** Paleontologist Heinrich Mallison from the Museum of Natural History in Berlin wrote the paper, which will be published in the upcoming issue of the Journal of Vertebrate Paleontology

Heinrich isn't the first person to suggest Tyrannosaurs' butt muscles made it fast. A 2010 paper by a University of Alberta paleontologist looked at Tyrannosaurus's bones and concluded that they could probably outrun every other dinosaur at the time.****

The long and the short of it is: Tyrannosaurs weren't horses or giant chickens (although they're related) - or even ostriches, the fastest critter on 2 legs today. So we don't have an instruction manual to tell us how they worked and how fast they could run. The best we can do is find better analogies and make better estimates.


Dinosaur Biomechanics. R. McNeill Alexander. Proceedings: Biological Sciences , Vol. 273, No. 1596 (Aug. 7, 2006), pp. 1849-1855
** doi: 10.1098/rspb.2007.0846 Proc. R. Soc. B. 7 November 2007 vol. 274
cc: Images adapted from M. Martyniuk and Wikimedia

Posted by: Winifred Kehl, Communications