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Re: tiny-armed theropods

Unless the reduced limb is clearly modified for functional reasons
(e.g. alvarezsaurids) I think it may be a red herring to concentrate
on what small limbs do to contribute to the success of adult
organisms.  Mass savings and cost of growth aren't immaterial to adult
organisms, but they generally apply pretty weak selective pressures.
During early patterning and organogenesis in ovo, however, is another
story.  Bone among the (if not the most) expensive tissue to produce,
and in an egg your resources are finite.  A reduction limb size there
would have a much larger material impact on how likely an embryo is to
survive during times of environmental stress.

Organisms are selected on in all phases of their life cycle after all.


On Wed, Oct 5, 2011 at 11:16 AM, Augusto Haro <augustoharo@gmail.com> wrote:
> Forelimb reduction as a mass-reduction strategy may conceivably be
> also useful for small theropods if these need velocity. This may not
> apply to those which seem to be the faster dinosaurs, ornithomimids
> (unless their slender arms actually decreased their weight by becoming
> slender), but can apply to likely similarly fast alvarezsaurids.
> Although I agree that forelimb mass was relatively small, it is
> possible that for the sake of velocity or weight-saving even small
> weight saving bears an advantage.

Scott Hartman
Scientific Advisor/Technical Illustrator
(307) 921-9750
website: www.skeletaldrawing.com
blog: http://skeletaldrawing.blogspot.com/