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Re: flight stroke (pretty short)



----- Original Message -----
From: "Waylon Rowley" <whte_rbt_obj@yahoo.com>
Sent: Tuesday, May 07, 2002 5:05 AM

> Hehehe, no that wasn't what I was implying. If the
> femur were held parallel to the presacral column, the
> feathers could fold or splay to the sides. Shouldn't
> be long before we can confirm or deny this.

Oh. Can we actually tell whether these feathers pointed laterally or
caudally? Anyway, if they pointed laterally and were used for gliding, then
this IMHO begs the question of what was at the leading edge then, when
nothing was sticking laterally out of the knees. The feathers themselves are
symmetrical.

> However, you loose some of the lift provided by that
> patagium by allowing air to spill out more rapidly in
> front. I'm trying to think of a way to balance the
> body AND keep your surface area maximized.

Does flapping keep the effective surface area the same? ~:-|

> > -- my prime
> > objection is: how does the animal get the idea
> > (consciously, by instinct, however) of flapping?
>
> No matter the scenario, you run into that very
> problem. Maybe gliders sense when their bodies are out
> of balance, and wave their arms in an attempt to
> steady themselves -

Does any living glider do that?

> The same way you would if you were
> trying to balance at the end of a diving board on your
> tiptoes.

I rather think of an airplane which adjusts its rudders by just a few
degrees and keeps them that way to change its angle to the ground. An
unexperienced pilot would have to play around with the rudders to find the
optimal solution, but still wouldn't do anything repetitive -- and that
fast --, I think. (But then, planes can't flap in the first place...)

> Exaptation clearly happens, but what makes
> the animal suddenly decide to use an organ in a novel
> way? Hell if I know.

Maybe when it doesn't realize that what it's doing is novel. :-) (A few
proposed examples are: flapping evolved from jumping and fighting in the
air -- the theropods realized afterwards that the more they beat up their
enemy, the longer they stayed in the air; FUCHSIA -- the theropods flapped
faster and faster and realized afterwards that they had left the water;
vertical running -- they kept on running after the tree had ended. :-) )

> > No idea how much lift (or drag, for that matter)
> > Archie's tail could produce. Certainly easy to
> > test, but I don't know if anyone has done it.
>
> It looks like a control surface to me, with that
> distal fan at the end.

Hm... it doesn't just have a fan at the end, unlike what the new dromie
appears to have, but almost the entire tail supports long feathers.

> The way modern birds use their
> retrices indicates this was precisely the purpose.
> Feathertail gliders also do this I've read.

Probable.

> I also think it's pretty strange that all of
> the flying groups seem to have convergently reduced
> their tail length, and that those who didn't are more
> terrestrial (like pheasants, and peacocks)

Various birds of paradise, paradise whydahs etc. have very long tail
_feathers_. There are still 2 genera or so of long-tailed bats, and I wonder
why pterosaurs evolved short tails so late (but twice).

> > To add some comments about the basic bird wing (as
> > opposed to the basic
> > neornithine wing), I wonder why there are no real
> > remiges on the upper arms,
> > just tertials to fill in the gap between the remiges
> > and the body. Such a
> > gap is not seen in any certain glider I know of.
> > It's not sure whether
> > *Archaeopteryx* or *Caudipteryx* even had tertials.
>
> Yes, that IS odd. Femoral feathers might have filled
> this gap,

Requires very, very long femora. We have such long ones, *Yandangornis* had,
but I can't think of others...

> or maybe the humerus was held closer to the
> body than we think during gliding? This would orient
> the feathers further posterior, near the center of
> gravity.

Sounds possible (indeed the humerus never points directly laterally in
birds), but wouldn't longer feathers evolve more probably? (Except if wings
are present before gliding evolves -- HOBHY.)

> Pulling the wings forward from that position
> to land

sounds plausible

> might also be a way in which the flight stroke
> evolved.

sounds implausible -- how do you get the repetition?

> I can think of several gliders that have
> evolved wings or patagia near the CoG. The Draco
> lizard, and *Sharovipteryx.*

May be more evidence that bird wings didn't evolve for gliding.