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Re: Lemurs and Feathers



> In a message dated 6/19/01 2:44:01 PM, david.marjanovic@gmx.at writes:
> << Underwater flight provides a scenario in which the flapping movement
(and
> the aero-/hydrodynamic wing shape etc.) can be perfected >>
>
> The problem with underwater flight is lack of fossil evidence.

I'll ignore that, like everyone else does :-> , given that the Jurassic
fossil record of pretty much all small terrestrial animals is extremely
poor.

> The
> progression from non-avian to avian forelimb occurred in animals that ALL
had
> long thin hind limbs. They were not swimmers (other than when forced to,
> perhaps) -- they were born to run.

IMHO all were capable of running, and swimming was not done with the legs.

> <<flight in air is apparently next to impossible with symmetrical and
> asymmetrical wing feathers>>
>
> So some people say.

&§&%§&%§?$&§§%. It was nearly midnight when I wrote that. Once more: "flight
in air is apparently next to impossible with symmetrical wing feathers".

> Here's a hypothesis: ALL fossilized dinofeathers have SOME degree of
> asymmetry. Hard to disprove, right? Poorly preserved, right? Ever plucked
a
> chicken? There's hardly a symmetrical feather on it. Why assume
dinofeathers
> started out symmetrical? Their scales already weren't. Most integumentary
> structures in nature are quite asymmetrical, including scales, scutes,
hairs,
> feathers, claws, teeth . . . um, have I missed any? The accusation of
> theropods having symmetrical feathers seems likely to fade away with the
> first specimen preserved well enough to give clear measurements of such
> details.

Here's another hypothesis. All recent flightless birds have symmetrical
feathers, right? (In ancient Egypt ostriches were the symbol of justice
because their wing feathers are perfectly symmetrical.) Same for
*Caudipteryx*, right? This seems to imply that if there's no selectionary
pressure favoring asymmetry, wing feathers become symmetrical.
I don't talk of millimeters here.

>    Based on a simple look around the animal kingdom, why not go with the
> majority? Asymmetry is plesiomorphic for MOST vertebrate structures,
period.

The keeled scales of snakes are symmetrical... lots of dinosaur osteoderms
are symmetrical... lots of vertebrate structures are. Statistics is IMHO a
poor argument here.

But that's irrelevant to start with!!! :-) Should wing feathers, for
whatever reason, have been asymmetrical like those of flying birds incl.
*Archaeopteryx*, then I need not explain how this evolved, and underwater
flight could have been easier from the beginning.