Re: Cost in Aquatic Birds (long)

["David Marjanovic" <david.marjanovic@gmx.at>]

----- Original Message -----
From: "Jaime A. Headden" <qilongia@yahoo.com>
Sent: Thursday, April 04, 2002 8:45 AM

>   The problem with this is that animals which take to the water for any
> form of flight, and have large limbs, tend to _reduce_ these limbs until
> they are short, stubby, muscular, and structurally unique. You don't see
> this in *Archaeopteryx*,

or in dippers,

> and in fact the broad structure of the wings
> would have been counter-productive to aquatic thrusting.

As in dippers.

> Archie just has not the equippage to do much of anything
> in the water.

Like a dipper. :-)

> Proposing an aquatic thrust theory for the development of
> aerial mechanics ignores the nature of the appendicular propulsors in
> living vertebrates, which are shorter and stubbier in the adapted forms.

For a bird Archie's wings are pretty short.

> <Why doesn't this destroy the whole hypothesis? -- I can simply assume
> that wings of considerable size were present even before that, and there
> was a selective pressure to retain them.>
>
>   The problem is is that the animal would have had these prior to entering
> the water. So why have them to begin with.

This is the _strength_ of the hypothesis. I can _decouple_ the evolution of
_wings_ and the evolution of _the wing stroke_. Why have wings? For brooding
sensu lato. And whatever sorts of display.

> Ebel's theory only works if the
> animal is a terrestrial form and has developed the larger arms

yep

> as an adaptation to increase in brachial-thrust.

I don't think so.

> This ignores the viscocity of
> water and the tendency to compensate by reducing the area of the wing and
> achieving similar thrust through muscular effort.

Just as dippers ignore it? :^)

> Elongation of limbs with
> the increase in the feathers is exactly the opposite effect,

Unlike Ebel, I don't think the arms elongated _after_ diving behavior
evolved, but before... for... brooding. :-)

> <In most of today's wing-propelled divers this pressure that keeps them
> >from evolving penguin-like flippers is the necessity to be able to fly.
> (Penguins, Great Auks and others have somehow managed do circumvent
> this.)>
>
>   Erm, I think you're taking dippers too far back. They are the exception.

I know they are the exception. That's what makes them fascinating. :-)

> They also have short, tapered wings.

No shorter than Archie's AFAIK.

> [...] the thunniform morphology of a bullet-shaped body,
> short tapered propulsive structures, and compact body without
> non-propulsive or aerodynamic protrusions is not just better, it's
> required, and a host of aquatic animals do this.

Do dippers?

> No animal has ever gone
> into the water, become so highly derived to acheive capable aquatic
> flight, then come back out and flown.

Looks like insects have done it: evolved tracheal gills, later flapped them
for swimming, later flapped them for skimming around while standing on the
water, as stoneflies still do, then flapped them for flying.
        "Became so highly derived" is not what I think happened to the
diving ancestors of birds; when you already have wings and laterally-facing
glenoids, it may largely be behavior, just as you wrote diving in dippers is
just behavior.

> Ihe case of the various flying
> fishes is different, as is that of *Isurus*, the mako shark.

Sure. (Flying fishes sort of glide, and do makos do anything else than just
jumping out of the water?)

> <I assume one or both of these caused the ancestor of all flying theropods
> to retain long wing feathers, at least during part of the year,> and to
> swim with them, as so many birds do today. (Many auks molt all their wing
> feathers at once and are then flightless for weeks.)>
>
>   Auks molt every other feather, retaining the ability to swim during the
> moulting phase.

Feduccia writes they molt all feathers at once... maybe just some species.

> However, what reason can you see that aquatic effects
> would no0t have reduced the arm as they do on any other animal that
> becomes adapted to swimming.

Then dippers are not adapted to swimming. Then maybe Archie was just as
little adapted to swimming. :-)

>   Or that confuciusornithids couldn't fly and the lack of a sternal keel
> indicates a problem of aerial maneuvering.

Why maneuvering?

> The penguin is the not the needed
> plan, it is required for the equitable flying thrust in an aquaeous
> environment. Or that is the conclusion produced from body types developed
> by underwater fliers, anyway.

Dippers haven't developed much.

> <Just like digits aren't necessary for a pike (correct? *Esox lucius*
> anyway),>
>
>   Like it has a choice in the matter ... lol.

Apart from all frogfish, I'm just pointing out that it still _can_ lead that
lifestyle.

> <digits bring an advantage in its way of life and can therefore evolve in
> an animal that occupies (sorry, makes up) this ecological niche.>
>
>   Not neccessarily. They are a solution to bottom dwellers, for muddling
> and maneuvering.

They are also a solution to those that need to move slowly through thick
vegetation.

> [...] I think
> the serrations must have been lost at some point, either as an adaptation,
> or because the teeth were too small for serrations to have an effect
> anyway. Should the former be correct, it suggests that all
> Maniraptoriformes didn't just start out looking like Archie, but also
> eating the same.>
>
>   Actually, only *Caudipteryx,* ichthyornithiforms, hesperornithiformes,
> and enants have this. Other forms have serrations, including
> *Protarchaeopteryx*, *Pelecanimimus*, and *Sinovenator*;

*Pelecanimimus*? Really? -- Forgot the serrations on the posterior teeth of
*Sinovenator*. Anyway, only a well-resolved phylogeny will be able to tell
whether they (and those of *Protarchaeopteryx* and dromaeosaurs) are a
reversal.

> microserrations have not been corroborated for *Archaeopteryx,*
> but neither have they been refuted.

The "cf. *Archaeopteryx*" teeth from Guimarota do have a few _tiny_
serrations on the anterior edge.