[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Re: The origin of flight: from the water up



   This interpretation is imaginative, of course, and
sounds appealing even to me, but I see some problems
with it. 
    If you look at a highly specialized sea-going bird
like a penguin, you can see what evolution favors in
semiaquatic maniraptors. The wings are stubby, the
feathers are more hairlike, and the body becomes
smoothed-out into an elliptical shape with a beak at
one end and some tiny feet at the other (presumably to
cause less hydrodynamic turbulence). Why would a
semiaquatic bird *want* large wings? It would be alot
of work flapping them underwater, as you can see in
diving birds with normal-sized wings. The penguin is
perfect, though. It just flaps those nubbins faster
and compensates. So, if your diving maniraptors spent
a good portion of their time hunting fish, I don't see
why evolution would allow them to keep their wings in
favor of feathery flippers. 
        As previously stated, pneumaticity may be a
problem. From their feathers to their bones,
coelurosaurs, as I'm sure you know better than I do,
had plenty of air in them. If you consider that there
was a gas layer beneath their feathers, it would only
be worse. If they oiled-up before going under I would
think there would be trapped air between the skin and
feathers. I can see birds using *a* pneumatic sac as a
swim bladder, but damn, that's overkill. It would take
a mighty strong theropod to swim around with the
equivalent of little balloons stapled all over it's
body. So, I would expect a reduction in pneumaticity
to occur. 
      Can a swimming theropod take to flight? Can it
reach an appropriate speed underwater with
normal-sized wings, and break the surface in full
flight? All the nature shows I've seen show birds that
have dove underwater coming up to the surface and
taking a a short rest before flying off with their
catch. Water is about 1000 times the density of air,
and drag forces are going to be a pain in the ass. 
      Anyway, I just see too many physical problems
with "flying out of the water" and the hypothesis just
complicates the issue more than it needs to be. We
already have nicely feathered arboreal maniraptors.
And with very little mental work I can see them
transitioning from gliding to powered flying. 
      They would hop from a branch, wings held nearly
vertical (parallel with eachother) with respect to the
ground. This would increase velocity. As they fell,
they would then extend the wings horizontal and begin
to angle the leading edge upward. This would give them
some lift. After a short bout of gliding, they would
allow the lift generated to push the wings back to
vertical. Add a little muscle power to this and you
get a flight stroke if I'm not mistaken. 
      The more I think about this scenario, the more
it reminds me of owl hunting behavior. It would be
interesting if maniraptors hunted from their perches
at night or in the late evening. They would need big
eyes and good balance/hearing, which is what we
observe in the fossils. Just had to add an extra
tidbit of speculation, forgive me :)

Cheers,
Waylon Rowley    


  

__________________________________________________
Do You Yahoo!?
Yahoo! Movies - coverage of the 74th Academy Awards®
http://movies.yahoo.com/