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Re: tiny-armed theropods

On 5 October 2011 21:21, Augusto Haro <augustoharo@gmail.com> wrote:
> 2011/10/5 Richard W. Travsky <rtravsky@uwyo.edu>:
>> Theropods have always looked unbalanced to me, esp if they are considered
>> with a full stomach. Not sure what the weight savings would be, tho.
> Good idea! But Paul stated that theropods, as other obligate bipeds,
> are especially inestable animals, and used this to argument to suggest
> that they achieved stability by walking at high velocity (which then
> supports seing obligate erect bipeds as possessing high metabolic
> rates). Velocity may thus help to balance the unbalanced theropod.
> Besides, he also supported the hypothesis that theropods had a
> relatively crouched attitude, which places the center of gravity
> forwards of the hip joint.

How would walking quickly forwards (all the time) help balance a
cranial CoM? You'd have to constantly be accelerating, otherwise no
constant balancing force. Most theropods CoM position seems to be
pretty cranial of the hip, somewhere around where I'd expect the
stomach and gut to be (paper coming out soon!). You would need a
relatively 'crouched' (i.e. inclined femur) posture to deal with that.
But it would be interesting to stick an ostrich on a forceplate before
and after a large meal (hint hint).