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

Re: Dinosaur color vision and evolution of feathers



Just to reiterate a point I’ve made previously, we also need to be careful with 
what we call “asymmetric”. Do we just mean feathers with anatomical asymmetry 
(i.e. one vane at all wider than the other)? If that’s the case, then it could 
probably appear via basic drift and/or pleiotropy. A feather with a vane ratio 
of 1.1 to 1 will not behave, mechanically speaking, any differently than one 
exact symmetry in a fluid interaction sense (though the wing folding idea and 
other such mechanical functions are different and, to the best of my knowledge, 
untested). The more extreme asymmetry seen in some (but not all) living volant 
birds should have an effect on aeroelastic stability and stall thresholds, but 
probably not steady state functionality.

Cheers,

—Mike


> On Oct 27, 2014, at 2:51 PM, Dann Pigdon <dannj@alphalink.com.au> wrote:
> 
> On Mon, Oct 27th, 2014 at 7:21 PM, Dr Ronald Orenstein 
> <ron.orenstein@rogers.com> wrote:
> 
> 
> 
>> A thought: is it possible that the aerodynamic properties of asymmetrical 
>> feathers could be
> 
>> related not to flight or gliding, but to display?  In other words - if rapid 
>> movement of banks of
> 
>> pennaceous feathers in the course of display has any significant energy cost 
>> associated with it
> 
>> (eg vigorous arm-waving displays) then an adaptation that would reduce the 
>> effect of air
> 
>> resistance on the cost of display movement might be selected for (especially 
>> if the display
> 
>> included leaping, parachuting etc). 
> 
> 
> 
> Or perhaps feather asymmetry improved the ability to fold display fans away 
> when not in use.
> 
> 
> 
> -- 
> 
> _____________________________________________________________
> 
> 
> 
> Dann Pigdon
> 
> Spatial Data Analyst               Australian Dinosaurs
> 
> Melbourne, Australia               http://home.alphalink.com.au/~dannj
> 
> _____________________________________________________________
> 
>