Re: Cost in Aquatic Birds (the big one)

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

----- Original Message -----
From: "Williams, Tim" <TiJaWi@agron.iastate.edu>
Sent: Thursday, April 11, 2002 11:03 PM


> > Thanks to HP Tim Williams for anticipating some of my questions and
> > thereby shortening this post. :-)
>
> No problem.  But - yikes! - how much longer would your post have been
> otherwise?

2, 3, 4 KB longer, I guess... who knows... anyway, it had 16 KB, and I've
seen (and written) longer ones; many shorter HTML posts are much bigger, HP
Tracy Ford can reach 21 KB for nothing. And who's Tom Clancy? :-)

> > Positive data exists for several theories, including the Hopp and
> > Orsen brooding hypothesis
> [snip]
> > it provides the BCF hypothesis with one for why wing feathers
> > and not a patagium evolved;
>
> We don't need to invoke a brooding --> flight scenario to account for
this.

I'm talking only about the wings here, not about flight :-)

> Birds appear to be only the flying vertebrates that we know evolved from
> bipeds.  (I think it's a safe bet that bats had a quadrupedal gliding
> ancestry, [...])

While it's for all practical purposes obvious that bats must have had
quadrupedal ancestors, it's not so sure those were gliders. Someone has
suggested onlist that they were arboreal leapers that caught insects in
mid-air with their hands. This scenario supplies an analogue to the
predatory stroke, and a reason for doing it repetitively in the air, but not
one for how the wings of bats evolved... the insect net hypothesis creeps
back... hm. Would be great if we found any sort of proto-bat. :-)

>  As such, the pectoral skeleton only was available to support
> the wing surface in birds.  This precluded the evolution of a membrane
> (patagium) linking the fore- and hindlimbs.

But not the evolution of pterosaur-style wings, respectively even more
extreme brachiopatagia, that link the hands with the torso.

> Besides, early birds and their forbears MIGHT have had a
mini-propatagium -
> though I'm aware that no fossil _Archaeopteryx_ or feathered
deinonychosaur
> shows a propatagium, AFAIK.

Personally I'd say that the pro- and metapatagia that recent birds possess
evolved after flight, to keep the wings in position with less muscle effort
and to put tendons into more effective places (there's one that runs from
the extensor process on the metacarpus straight to the shoulders, right?).
None of those fossils shows one, but I can't tell how easily they could have
been preserved (but I think they'd have left impressions in the Berlin
specimen).

> > Not to mention the behavior of adult stone"flies" (which are
> > basal Pterygota).
>
> Last I heard, Plecoptera (stoneflies) are considered basal Neoptera.
> Odonata (dragonflies, damselflies), Ephemeroptera (mayflies) and a bunch
of
> extinct orders are basal Pterygota (winged insects).  Neopterans can fold
> their wings across their abdomen; non-neopteran pterygotes like
dragonflies
> cannot.  (I majored in entomology, but it's been a while so insect
taxonomy
> may have changed.)

Sounds all plausible... must find a textbook, as I didn't know the term
Neoptera. Anyway, I've seen stoneflies fold their wings. --
http://tolweb.org/tree?group=Neoptera&contgroup=Pterygota&dynnodeid=7639
shows an awful polytomy and the optimistic sentence "The placement of the
plecopterans, embiids, and zorapterans are perhaps the most enigmatic." :-)