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Re: tiny-armed theropods



Ralph Chapman <ralphchapman@earthlink.net> wrote:

> Let us also remember that there is a great chance that there is not a single 
> explanation for the
> different lines. What may be, at least in part, a developmental strategy for 
> tyrannosaurids may
> not work at all for earlier theropods. Bipedalism may simply be preadapted 
> for the generation of
> various mechanisms for fore-limb reduction or, more probably, fore-limb 
> variation which then
> leads to the bird oriogin stuffola.


Agreed, on the whole bird origin stuffola thing.  The reason why
dinosaurs became bipedal in the first place isn't entirely clear.  The
shuvosaurids made the same shift to bipedality, and the function of
their forelimbs isn't clear.  Overall, the forelimbs of _Effigia_ (big
scapula, but tiny hands) look about as useful as tits on a bull.  Much
the same is true for many theropods.  Nevertheless, once released from
its ancestral role in quadrupedal locomotion, the theropod forelimb
was 'free' to evolve into all sorts of interesting things.  I would
say that the reason why the forelimb transformed into an avian wing
was *because* it was freed from its ancestral theropod role in
predation.






Cheers

Tim