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        I was looking at "Diatoms to Dinosaurs" today and the book 
confirmed what I started thinking after reading sections of "On Growth 
and Form" : That sauropod vertebrae, by virtue of their extensive 
excavations, are in effect I-beams. I think it was page 87 and a cross 
section of Camarasaurus. Even if the overall mass of the bone was not 
reduced, the strength would have been increased. Tubular bones serve the 
same purpose, they are in effect circular I-beams.
        This isn't of course all the answer, as things like Compsognathus 
have hollow bones too and they were not under the pressures to increase 
the strength-to-weight ratio that birds were (unless George is right) nor 
the pressure to increase this ratio that sauropods would have been. But 
it is part of it I'm sure. 

        It also had a little picture detailing the truly extensive 
variety of patagia connecting feet to wings and feet to tail in the 
Chiroptera; it does not seem unlikely that pterosaurs could have been 
similarly diverse. 

        I am still trying to figure out the Chinese longfeather bird. I 
had originally thought of the african whidda (widow?) birds which have 
very long tails used to attract females. However, they are not that similar. 
That bird has barbules all the way down the rachis, and a thin, flexible 
rachis, quite unlike the very stiff-looking, mostly bare rachi of the 
longfeather bird, and something like four, not two of these feathers. The 
resplendant quetzal is much the same.  The standard-winged nightjar seems 
quite similar but the rachi are very  flexible (and they are on the wings). 
The longfeather birds, again, had rachi that  looked quite stiff and did 
not appear to be bending at all, and appeared  rather thick as I recall.
Both birds shared this feature so they would  both probably have to be males 
if it were a sexual feature-  not impossible. For all I know it 
was just a breeding form of  Confuciusornis, I didn't take a good look at 
the skull  and I saw a restoration of that bird with a similarly short 
tail. But if no dimorphism appears, it could concievably be aerodynamic, a 
double version of the rhamphorhynch tail. That would be weird. We will 
see in a few months I imagine, and I'd tend to go with it as a sexual 
feature but I'd be open to the aerodynamic possibility. But would TWO 
long horizontal -----------------<<<<<<>  
"tails" like this ( they actually were angled apart a bit ) be very good 
for maneuvering? I suppose it might work similarly to the forked tail of 
the swallow if that's aerodynamic (is that dimorphic?).