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Re: Lemurs and Feathers



I wrote:

> >I still prefer HP Tom Hopp's idea that wings evolved for brooding, and
> >Klaus
> >Ebel's idea that the wingstroke evolved for underwater flying is still
the
> >only explanation for the wingstroke that I know.

HP Tim Williams wrote:

> Please.  Tell me you're kidding.

Sorry to disappoint you, er.. erm... ;-]

> >Won't happen in a parachuter, IMHO.
>
> Why not?  Flapping the primordial wing may do wonders for increasing
thrust
> and improving maneuverability.

When it's sophisticated enough, IMHO, but not earlier. For maneuverability,
rather slight movements of e. g. the hands should be enough, and thrust in a
glider... just jump off with more force! :-) (Not to mention that a
parachuter tries to decrease thrust by definition.)

HP Dinogeorge wrote:

> << Won't happen in a parachuter, IMHO. Any more plausible ideas? :-) >>
>
> Never say never, particularly in paleontology and in evolutionary
scenarios.

I didn't :-> -- OK, but I do think it is improbable, and my patchy knowledge
of the literature (including this list) has so far not brought to my
knowledge a plausible idea of how bird wings and the wingstroke should have
evolved in a glider.

> How feathers/wings for brooding lead to a flight stroke (and not simply to
> better brooding) is quite obscure to say the least,

Sorry if I didn't made my point clear enough ( ~:-| ). AFAIK nobody,
including myself, has ever said that brooding can lead to a flight stroke. I
just say that it is the IMHO most plausible explanation so far for how bird
WINGS, _NOT FLIGHT_, evolved. (And why nothing else, like pterosaurs or
bats, has wings of that sort.)

> not to mention underwater
> "flying," which would in the long run have led to all birds being like
> penguins or Hesperornis.

Surely not like *Hesperornis*, which was a foot-propelled diver!
Why they didn't all end up being like penguins might mean that that niche
were occupied (plesio-, ichthyo-, pleurosaurs, crocs, champsosaurs, what
have I forgotten?; when penguins evolved there were only basal whales, not
even seals)... and see below.

> Probably went the other way, or at best evolved in
> tandem: easier to get from flight to brooding and underwater flying than
vice
> versa.

Of course underwater flight has evolved from air flight several times,
without, it seems, too many difficulties. Evolution in the other direction
probably is more difficult, but it only "needed" to happen once... :-)

The most "far-fetched" point -- and IMHO the point without which it
collapses completely -- of Ebel's paper is that underwater flight evolved in
a diving theropod. Well, when an animal that is equipped with complete
wings*** begins to dive, it will probably use its wings -- what else? -- for
propulsion, and if it has the forelimb/pectoral anatomy of a theropod, the
required movements will probably look a lot like underwater flight.

***Ebel, not knowing HP Tom Hopp's hypothesis (Ebel's paper is 2 years
older), has assumed that the theropod that began diving was fully feathered
but didn't have wings, and that wing feathers developed only for underwater
flight. This is indeed highly unlikely, the outcome of this might look more
like the old interpretation of *Compsognathus "corallestris"*, or even like
a penguin. But if wings are already in place, and there is a selective
pressure to keep them (for brooding), then an underwater flyer is much more
likely to result, IMHO.

More in older threads (largely December 2000, January 2001).