Re: Thou Shalt Not Climb!

[Tim Williams <twilliams_alpha@hotmail.com>]

Jaime Headden wrote:

>   More than likely, the animals were in trees before the selective 
> advantage
> for arboreality became apparent. Not even *Archaeopteryx* is _arboreal_, 
> though
> it was certainly scansorial. All other basal birds, begining at least with
> *Confuciusornis*, appear to be arboreal, with derived hindlimb for
> branch-sitting (maybe not "perching" per se) and reduced forelimbs for
> climbing, etc., while birds antecedent in anatomy seem to be a lot less
> inclined to the trees.

Jaime, out of interest, could you (briefly) describe what anatomical 
features in the hindlimb distinguish "branch-sitting" from "perching".

> Nearly all the long-tailed Liaoning birds have ropbust
> hindlimbs and the "scampering" forelimb structure, leading one to suspect a
> form of four-legged tree-climbing habitus with equal measures on the 
> ground, in
> the rocks, or in the trees, without any selective advantage (yet) for one 
> or
> the other.

Can you explain exactly what is meant by a "scampering forelimb"?  In other 
words, what characters in the forelimb suggest that it was used for 
scampering?  How are these forelimb characters different from characters 
associated with (say) predation?

BTW, I don't disagree with the idea that _Archaeopteryx_ and other basal 
avians could have (and did) climb up trees.  I'm just intrigued as to how 
the anatomy of _Archaeopteryx_ supports this interpretation.

Cheers

Tim

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