RE: the reason I asked about maniraptor limbs

[Tim Williams <twilliams_alpha@hotmail.com>]

Anthony Docimo wrote:

> Based on information I gathered from the answers to my question earlier in 
> the week (last week?),
> I made this sketch....
>
> http://www.deviantart.com/deviation/55865595/
>
> ...and I'm wondering if such a difference between the wrist and ankle is 
> plausible, before I try making a final version of the tree dino.
>
> (basically, for the hands, lift your hands up and clap once - the tree 
> dinos can't clap, but their palms do face each other.....the ankles, 
> however, have only the degrees of flexion as found in conventional 
> (non-avian) maniraptors)
>
> thoughts?

I thought this was true for all maniraptorans.  The palms face inwards, but 
the hindlimbs are held vertically and restricted to parasagittal movement.  
Whether this combination is suitable for trunk-climbing is a totally 
different question.  I believe Chatterjee floated this idea (or a similar 
idea) in his book - and additionally suggested that the stiff tail could be 
used as a brace during climbing.  But the idea of trunk-climbing 
maniraptoran has been received with skepticism by some authors.  For 
example, here's what Padian (2003) wrote...

"Now, consider (as Paul and Chatterjee do) the hypothesis that flight 
evolved in the trees, which requires these animals to climb trees.  As Paul 
points out, this is no problem for most animals if they have prehensile 
hands or sharp claws.  (However, it?s not this simple either.  Goats can 
climb trees by hooking their hoofed ??hands?? over branches, but they 
couldn?t scale a naked tree trunk: there?s a difference between ladderlike 
branch climbing and scansorial trunkscaling.)  But the geometry of the body, 
the features of the hands and feet, and especially the musculature and 
kinematics of the limbsmust be considered.  Chatterjee (1997) provided 
diagrams of protobirds and early birds climbing trunks to show a possible 
range of motion required, but he did not analyze the musculature to see if 
it was consistent with and capable of these motions.  Nor did he analyze 
whether a forelimb whose major function is protraction, retraction, and 
rotation (in flight) can also effectively supinate, adduct, and retract in 
that position to achieve climbing "

Cheers

Tim

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