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Re: Feathers vs patagia



> David,
>      Well, I do look forward to seeing your paper.

So do I  B-( . I've just mailed to the editor asking what has happened
(maybe it is published, and snail-mail just hasn't carried it to me yet).

> However, I'm not sure your objections to Larry's ideas are necessarily
> valid.

How could you (nitpicking)? This is neither mathematics nor logics... ;-)

> He isn't saying that birds evolved from any of the advanced
> pterosaurs you are describing, but forms which were far more primitive
which
> haven't been found (or perhaps sitting unrecognized in some museum
drawer).
>      I can contemplate such an ancestral form (perhaps a little more
> pterosaur-like than birdlike) gliding from gymnosperm to gymnosperm (be
they
> cycads, conifers, or some other gymnosperm). One line goes the pterosaur
> route, another goes the bird route, and the intermediates go extinct. And
> if I understand Larry's ideas correctly, theropods are secondarily
> flightless birds (in agreement with BCF theories).

Oh. OK. Still I think the transition from a glider to a (flapping) flier is
next to impossible for physical reasons. I must admit that I don't have a
better idea on how bat flight evolved than from gliding, but anyway we'd
expect to see a large brachiopatagium in birds instead of wing feathers.

>      I don't know if pterosaurs and birds had a primitive gliding common
> ancestor, but I think it is a good idea to investigate such possibilities
> (just as you are apparently doing in developing some other possible
> scenarios).  Whether Larry is wrong or right, I don't think his reasoning
is
> teleological, at least in the ways you seemed to be pointing out.  If they
> do have a common gliding ancestor, I suspect it would be more
pterosaur-like
> than birdlike.  Anyway, looking forward to your paper.
>                     -----Ken

I don't want to accuse him of spreading teleological beliefs, I only think
that he might (as I have repeatedly) have run into this trap without noticin
g it. I just can't think of any selectionary pressure leading to the
reduction of a sophisticated wing membrane (more complicated than in bats)
in favor of wing feathers; more on the improbability or impossibility of the
glider-flier transition in my paper :.-( and the references cited therein,
like the paper by Klaus Ebel, the ref of which I have sent to the list
yesterday (or today in the morning, on some other continents). (In this
paper, there's the maths and physics!)

However, I think HP Larry Febo has noticed some valid synapomorphies of
Ornithodira (Pterosauromorpha + birds sensu BCF). He has just mentioned
offlist that the supporting rods of pterosaur wings are keratinous and
hollow like feather keels; this supports the hypothesis (developed on this
list, I think) that protofeathers are a synapomorphy of Ornithodira and that
pterosaur hairs and wing rods may be feather keels. The difference between
our hypotheses in this point is little more than character polarity.

:-)

********************************************************
May G. W. Bush stay US president for long B-) . Exactly since he has been
designated (rather than elected...), the Euro is rising (I won't speculate
here about the causes B-) ). Yesterday it was already at 0.9543 US$,
tendency further rising... Ordering books at Amazon thus becomes cheaper and
cheaper. :-)