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Re: Flight SPECULATION
On Sun, 3 Dec 1995, Rob Meyerson wrote:
> >>G.O.s arboreal origins idea has a degree of=20
> >>plausibility, but I'll bet you could construct an argument, or a=20
> >>thousands arguments of equal plausibility for a cursorial origin of=20
> >I have yet to see even one.
> How about this: The theropod that evolved flight did so along a highly=
> irregular land surface (like a rocky shoreline). Flight is used in pursuit=
> of prey, where the theropod can simply glide over gullies, while it's prey=
> has to take the long way across (down and up). Similar evolutionary=
> pressures as with the aboreal hypothesis, but with a cursorial origin.
Bats almost certainly evolved in the trees, and it isn't hard to
see their ancestors as being something like flying squirrels or colugos.
Pterosaurs also most likely evolved in the trees, cursorial origins don't
seem to work too well for them. (I've seen and read all I can get and I
don't buy that these guys were bipeds. As Wellnhofer
notes, the head of the hip isn't even at a 90 degree angle, and the hip
sockets open out and up, not straight out) The vast majority of gliders
(assuming gliding is a stage on the way to flight, which seems logical enough)
are arboreal, though I have heard of a flying squirrel that lives on rocks
and cliffs- but then again, it evolved originally in the trees. There aren't
any modern cursorial gliders, either. Cliffs are just a lot more
dangerous, too. Moss, ginkgo leaves, humus and conifer needles are a lot
softer than sharp, jagged rocks. And it's easier to grab onto trees than
rock faces, for another thing, and if you miss, there's a lot more
branches down below.