[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,
Indeed. I really wait for an Early or Middle Jurassic site with fossils the
quality of Messel or Sihetun. :-)
> Why would a
> semiaquatic bird *want* large wings?
Because it still needs them for other purposes, such as brooding. Unlike a
penguin. Big wings mean more room for eggs which in turn means either bigger
or more eggs which in turn means more surviving offspring. It's a very
simple case of natural selection.
> It would be alot
> of work flapping them underwater, as you can see in
> diving birds with normal-sized wings.
Nevertheless many birds do just this for a living.
> As previously stated, pneumaticity may be a
> problem. [...] 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.
When the theropods specialize in this behavior instead of staying more
generalistic... like a dipper. AFAIK dippers are as extremely pneumatized as
any passerine, and much more than a basal coelurosaur.
> 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.
I don't know anymore whether I've seen that on TV, but Feduccia mentions
many species of auks and petrels that fly straightly through waves. Haven't
seen lots of dippers on TV.
> 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.
Arboreal? Do we? Except for the aye-aye analog which may be very close to
Pygostylia (I won't say why I think so, and my evidence is very limited
> And with very little mental work I can see them
> transitioning from gliding to powered flying.
Trap snapped. It requires immensely much mental work to get from gliding to
flying. We've had that discussion often enough, I think... that transition
is probably impossible, as flapping destabilizes a glider (screws up its
angle of attack and all that). No living glider flaps. Recently even a
speculation has been uttered about how bats may have evolved flight without
a gliding phase.
> They would hop from a branch, wings held nearly
> vertical (parallel with eachother) with respect to the
> ground. This would increase velocity.
Requires dorsally oriented glenoids (or extremely flat ones, like in apes) a
priori. Where do they come from?
> As they fell,
> they would then extend the wings horizontal and begin
> to angle the leading edge upward. This would give them
> some lift.
Anyway, such a strategy is said to be common among gliders -- first a short
fall to increase velocity, then the real gliding.
> After a short bout of gliding, they would
> allow the lift generated to push the wings back to
And then they fall again. Counterproductive.
> The more I think about this scenario, the more
> it reminds me of owl hunting behavior.
Very superficial. Owls use highly sophisticated combinations of parachuting
and flapping that can only evolve in a good flier.
> It would be
> interesting if maniraptors hunted from their perches
Where are the non-pygostylians with perching feet? I can't see any. Not
Archie, not *Microraptor*, not *Caudipteryx*. And in chicken embryology the
big toes migrate downwards and lengthen after having started in the
classical position seen in *Tyrannosaurus*.
> at night or in the late evening. They would need big
> eyes and good balance/hearing, which is what we
> observe in the fossils.
I wouldn't consider that special among predators.
Anyway, you are right in that a strong argument for me is purely negative:
the lack of plausible alternatives to FUCHSIA. Think some up :-)