[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

RE: the reason I asked about maniraptor limbs



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

_________________________________________________________________
PC Magazine?s 2007 editors? choice for best Web mail?award-winning Windows Live Hotmail. http://imagine-windowslive.com/hotmail/?locale=en-us&ocid=TXT_TAGHM_migration_HM_mini_pcmag_0507