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Re: tiny-armed theropods

Ooh, hang on, sorry. CoM is ventral, so you'd need to be braking to
cause inertia to exert a pitch-up moment on the trunk. Forward
acceleration would tend to cause a nose-down pitch. So to avoid
falling over by acceleration alone, you'd need to not only be
constantly accelerating, you'd need to be doing it backwards.

On 6 October 2011 10:12, Vivian Allen <mrvivianallen@googlemail.com> wrote:
> 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).