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T-rex leg length & walking



Blaise wrote:

>I'd like some clarification regarding the issue of rex's leg length as
>mentioned in The Ultimate T-rex. First, how is it that 2 paleontologists
>(names forgotten, Horner v Currie?) can arrive at 2 different conclusions
>regarding bone length? Were they looking at the same specimen? Could
>differences have something to do with growth/age of specimen? If the
>thigh and shin are the same length, does that mean rex could both run and
>walk? Second, how can walking be derived? Can't walking simply be seen as
>slow running? Derived from what?

Not having seen this at first hand, I can take a stab at it.

When trying to, ascertain movement limitations in dinosaurs, the usual
method uses the "hip height" (h) measurement - i.e. from foot to hip.  Now
this is not as straightforward as it seems, since the bones of the leg are
separated by cartilage and the leg is not held perfectly straight in life,
but - especially in bipedal dinos - was held flexed at the knee.

Hip height can be calculated in a number of ways.  One is to simply measure
the bones, thus h = (L femur + L tibia + L metatarsal III) = 9%
(the 9% is for cartilage).  This however does not take into account the
flexure of the limb in life.

Another way is to use the Foot Length (FL) in trackways.
Here h = 4.5 FL where FL<25cm, and h = 4.9FL where FL>25cm

A third way is to use Pace Length (PL) from trackways.
Here PL = 0.65h

It all depends on what calculations they used.  Each will give differing
results, and as a consequence different speeds.

Chris

cnedin@geology.adelaide.edu.au                  nedin@ediacara.org
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Many say it was a mistake to come down from the trees, some say
the move out of the oceans was a bad idea. Me, I say the stiffening
of the notochord in the Cambrian was where it all went wrong,
it was all downhill from there.