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re: "running" elephants

David Marjanovic <david.marjanovic@gmx.at> wrote:

quoting Richard Forrest:
> > To model the locomotion of a sauropod dinosaur on that of an elephant
> > on comparable top modelling the locomotion of an elephant from
> > something weighing about 300 kilos - a small horse, or a cow - which
> > can do all sorts of things elephants can't.
> =======================================================

David Marjanovic <david.marjanovic@gmx.at> wrote:
On the other hand... to model the locomotion of an adult elephant on that
of a 100 kg newborn elephant is not that bad AFAIK. (I'm not sure if young
elephants just manage to gallop, though. I've seen photos that may show
the one in the zoo of Vienna galloping...)

No, I've looked at even baby elephants and they all do the same thing. No aerial phase, no gallop/trot, just the "singlefoot in lateral sequence with lateral couplets" (standard Hildebrand terminology) that is typical of walking: like a dance step, 1-2, 3-4 from left hind then front, pause, right hind then front. A gallop is very different. But yes, small elephants use motions very similar to large elephants; it's just that duty factor is lower and Froude number is higher; stride length is lower, stride frequency higher. Roughly same absolute speed regardless of size from ~age 2. Not sure about elephants >3000 kg yet, which is all we've studied in terms of healthy, active elephants (we worked with some big ones in America ~5 tons but they were couch potatoes).

quoting me:
> IF elephants use a bouncing (biomechanically running) gait, such as
> Groucho running (a bouncing gait with more flexed limbs), the principle
> applicable to dinosaurs would be that even large dinosaurs might have
> been able to extend their range of locomotor performance by using a
> similar mechanism.

David Marjanovic <david.marjanovic@gmx.at> wrote:
Now I am using elephants as a model for dinosaur locomotion... but
considering the permanently flexed legs of even *Tyrannosaurus*, wouldn't
it automatically have used such a bouncing gait above normal walking

Can of tyrannoworms...
I still don't know what people mean exactly by "permanently flexed legs"; is this some horrible gait pathology? Poor things. I prefer to speak in relative terms. If one means that Tyrannosaurus had more flexed leg joints than an elephant, I might agree, to a degree, but that means nothing "automatic" about gait to me. I would not say that such a bouncing gait was impossible, but I wouldn't assume it either. If one looks closely at the elephant videos, they increase leg flexion a bit (esp. hindlimbs) when "running", so I wouldn't assume one limb orientation for any one animal in all gaits or label one animal as being stereotyped with one "permanent" limb orientation. Birds, etc. do not maintain a single set of joint angles from slow walking to "Groucho running" to all-out running.

Just my take,

=========================================== John R Hutchinson NSF Postdoctoral Research Fellow Biomechanical Engineering Division Stanford University Durand 209, BME Stanford, CA 94305-4038 http://tam.cornell.edu/students/garcia/.trex_www/naturepaper.html http://www.stanford.edu/~jrhutch/fast_elephants/wanalee/index.html (650) 736-0804 lab (415) 871-6437 cell (650) 725-1587 fax ===========================================