Re: Archaeopteryx and Flight

[Chas Bedford <chasbed4d@chas.demon.co.uk>]

>Yes, but that is my point. If the traits needed were not there BEFORE
>they went into the trees, then they WOULD have all the gliding char's of
>a brick (or at least of a small-medium sized animal). They must have had
>these characteristics (ie. elongated feather-like structures, probably
>some gliding ability) BEFORE they took to the trees.

At the risk of attracting some flaming; I wonder if the evolution of flight
is such a big deal. Powered flight seems to have evolved at least four
times independantly (insects, pterosaurs, bats and birds) and gliding
flight more often than that. I am aware among modern animals of gliders in
the mammals, reptiles, amphibians and fish (BTW, I doubt if the fish
started gliding from trees :->)

The thing that really fascinates me about Archie and birds is the evolution
of feathers. Feathers allow you to construct a lightweight robust wing with
a decent aerofoil section, unlike membranes which can only give a
single-surface sail. It the differerence between a basic Rogallo
hang-glider and a 'proper' aircraft wing.  Feathers are also reasonably
self-healing which means you can exploit protective habitats. Imagine a bat
diving full speed into a thorn bush; it would tear its wings pretty badly.

>I can't see the
>proto-archies climbing featherless into the trees and THEN
>developing long fragile feathers. There is too much danger in damaging
>them when climbing around, and they would tend to get in the way too much
>for the advantage of _occasionally_ having to leap from a tree to save
>itself to have much effect.

>My only thought is
>whether it is more likely that these initial processes developed before
>or after the ascent into the trees. I tend towards before since I can see
>little purpose for the interim steps when living in a tree.

I agree with you on that, but wonder what the original purpose of feathers
might have been. Thermal insulation seems obvious, but the best feathers
for that purpose are downy - look at an ostrich - rather than rigid flight
feathers. Physical protection is a possibility. I've already mentioned the
self-healing characteristics; and I've heard of old Japanese feather armour
which was surprisingly light and effective. I also recall hearing a
suggestion that an armful of rigid feathers makes a good insect net.
Perhaps some of the professionals out there could weigh in with current
thoughts on this.

Happy New Year to all.

_____________________________
Chas Bedford

chasbed4d@chas.demon.co.uk
chasbed4d@cix.compulink.co.uk