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Re: secondary flightlessness



Dinogeorge@aol.com wrote:
> 
> You might be right about bats and pterosaurs (I don't think so, because the
> fossil record is really, really lousy when it comes to preserving the small,
> arboreal forms that were probably transitional between bats or pterosaurs and
> their flightless ancestors),

I agree. Preservational bias would tend to work against exactly the
sort of small, delicate arboreal forms that might have formed such
"transitional forms". I have always been a punctuated equilibrium
person myself. Something is either well adapted to what it does or
it doesn't exists. The term "transitional form" tends to suggest some
sort of directionality, being somewhere between one state and another,
which to me at least smacks of creationism (sorry Mickey - the dreaded
C word). I can't see the usefulness of being sort of able to fly and
sort of not. Hence my belief that such evolutionary leaps are rapid
(geologically speaking of course). Natural selection doesn't grant
pardons because a species swears that, in a few million years more,
it will be really well adapted to a new niche.  :)

>... but there >are< plenty of transitional forms for
> birds and pre-birds. We call them theropod dinosaurs. This fact alone strongly
> supports a lengthy period of evolution of avian flight.
> 
> DD3

And yet if "birds came first" (however one defines "bird") then surely
they pre-date the earliest theropods? Suggesting a rapid Triassic
appearance perhaps of feathered flying forms, with preservational
bias favouring younger sediments and hence masking early (and rapid)
evolutionary innovations? This is not my personal stance, but surely
it is a possibility.
-- 
____________________________________________________
        Dann Pigdon
        Melbourne, Australia

        Dinosaur Reconstructions:
        http://www.geocities.com/capecanaveral/4459/
        Australian Dinosaurs:
        http://www.alphalink.com.au/~dannj
____________________________________________________