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Re: Sifaka and Chukar Behavior: Trees Down or Ground Up?



On Sun, 26 Jan 2003, Dann Pigdon wrote:
> "Jaime A. Headden" wrote:
> >  [BIG SNIP]
> 
> >  What this appears to be, rather, is that one group of small, predatory
> > theropods in the trees became adapted to gliding independantly of all
> > other  avian-style theropods, and that in no way do these finds support
> > either the trees down or the ground up hypotheses. Merely an interesting
> > sideline.
> 
> Preaching to the converted, here. I've attempted to correct the problems
> with the top-view reconstruction in the paper (tail feathers too large
> and too proximally located, leg elements in wrong proportions, etc). You
> can see my humble attempt at:
> http://www.alphalink.com.au/~dannj/temp/mgui_silhouette.gif
> 
> To me, this looks like a glider that used its legs to provide lift only,
> leaving the forelimbs free to provide control (and perhaps occasional
> thrust), with a bit of extra lift thrown into the bargain. I've assumed
> no feathers attached to the humerus, and have the tarsal feathers
> extended (according to HP Paul's idea of muscular control, which I also
> considered possible).

Ok, completely off the wall and unqualified and layperson's observation
here sparked by your silhouette.

The tail isn't going to provide the kind of control that tails of more
modern birds provides. However, it looks like this critter could've kept
its legs together and performed some of the same functions a modern tail
could. Plus, spreading its legs a bit could approximate a split tail.

IOW, it adjusted its leg positions to get different flight
characteristics.

Where's a wind tunnel model when you need one?