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Re: [dinosaur] Jianianhualong, new feathered troodontid from Lower Cretaceous Jehol Group of China (free pdf)



Dann Pigdon <dannj@alphalink.com.au> wrote:

> Could vein asymmetry have originally evolved to aid in folding the 'wing' 
> fan? Ostriches appear to
> have symmetrical feathers on most parts of their bodies, however some of 
> their wing feathers
> seem to be asymmetrical. Perhaps that helps the feathers to slide over each 
> other when folding
> or unfolding the forelimbs?



Yeah, good question.  A while back, Thulborn and Hamley (1985)
proposed that vane asymmetry in _Archaeopteryx_ had nothing to do with
flight, but reflected "an economical method of wing design".  Under
this interpretation, _Archaeopteryx_'s vane asymmetry was a way of
avoiding excessive overlap (imbrication) of wing feathers without
leading to large gaps (slots) opening up between these feathers, in
order to maintain continuity of the wing surface.  To put this in
context, Thulborn and Hamley proposed that _Archaeopteryx_ used its
wings for heron-like canopy fishing, not for flight.  I don't agree
with their ecological hypothesis (which involved a flightless and
aquatic _Archaeopteryx_), but it at least shows that someone has tried
to account for vane asymmetry in a non-aerodynamic context.


Reference

Thulborn, R. A. and T. L. Hamley (1985). A new palaeoecological role
for _Archaeopteryx_. In: M. K. Hecht, J. H. Ostrom, G. Viohl, and P.
Wellnhofer (Eds.), The beginnings of birds. pp. 81-89.