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Re: Power-walking tyrannosaurs



In a thousand words - the 2nd variation put together by Jean-Pierre and
me:
http://vimeo.com/1656581

Or am I mistaken? I haven't gotten a chance to read through the paper
yet!

-Jonas Weselake-George


On Tue, 08 Nov 2011 11:51:28 +0100
Vivian Allen <mrvivianallen@googlemail.com> wrote:

> Congrats Heinrich! Looks like this is making a splash!
> 
> Viv
> 
> On 8 November 2011 04:53, bh480@scn.org <bh480@scn.org> wrote:
> > From: Ben Creisler
> > bh480@scn.org
> >
> > An online article on the Nature site and the abstract from the SVP,
> > challenging Alexander’s calculations for theropod locomotion:
> >
> > Tyrannosaurs were power-walkers
> > http://www.nature.com/news/2011/111107/full/news.2011.631.html
> >
> > MALLISON, Heinrich, Museum fr Naturkunde - Leibniz Institute for
> > Research on Evolution and Biodiversity at the Humboldt University
> > Berlin, Berlin, Germany
> >
> > FAST MOVING DINOSAURS: WHY OUR BASIC TENET IS WRONG
> >
> > Locomotion speeds of dinosaurs are often calculated from
> > ichnofossils, using Alexander’s  formula that is based on data
> > mainly from mammals and birds. Results indicate that dinosaurs were
> > rather slow compared to mammals. Inaccuracies due to errors in hip
> > height  estimates and other factors are expected, but the method is
> > generally accepted to deliver at least "ballpark figures". However,
> > in nearly all dinosaurs except theropods the hind limbs differ
> > significantly from both mammals and birds in the distribution of
> > maximal joint torques possible. Is it biomechanically sound to
> > apply the formula under these circumstances? A detailed assessment
> > of dinosaur limbs, using musculoskeletal modeling in SIMM and
> > Computer Aided Engineering (CAE) kinetic/dynamic modeling, taking
> > gravity, mass distribution and inertia into account, indicates that
> > a basic tenet of Alexander’s formula, the proportional relationship
> > between stride length (SL) and stride frequency (SF) seen in
> > mammals and birds, is unlikely to have existed in non-theropod
> > dinosaurs, and may have had an unusually low slope in theropods.
> > This means that speeds calculated from tracks are the slowest
> > speeds at which the animals have moved, but may be significantly
> > too low. We may therefore not expect to gain information on the top
> > speeds of dinosaurs from tracks at all. Skeleton-based analyses can
> > suffer from similar uncertainties, because large limb excursion
> > angles as seen in quickly moving mammals create high forces in the
> > limbs. Usually, similar limb kinematics are assumed for dinosaurs.
> > However, if dinosaurs combined high SFs with short SLs, they were
> > able to move far faster for given maximal forces in the joints than
> > previous models suggest. The modeling results from SIMM and CAE
> > suggest that dinosaurs used much higher SF/SL ratios than mammals,
> > achieving absolute speeds in walking gaits that force same-size
> > mammals into running gaits.
> >
> >
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