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Re: flight stroke (pretty short)



David Marjanovic wrote:

> Oh. Can we actually tell whether these feathers
> pointed laterally or caudally? Anyway, if they 
> pointed laterally and were used for gliding, then
> this IMHO begs the question of what was at the
> leading edge then, when nothing was sticking 
> laterally out of the knees. The feathers themselves
> are symmetrical.

As for the first question, I assume we could look at
their attachment points on the thigh to try and
determine if they would be good for
gliding/parachuting. If the humerus were held against
the trunk, it would slightly overlap the knee in most
avepectorans, so, it may have formed a coherent
surface. Once good-sized tertials evolved (this is
assuming they *aren't* present in Archie) they would
replace the femoral array. I would like to know how
long these feathers are in the long-tailed theropod.
John Ruben made a comment about them being half the
tail length....which I doubt, but if true would be
substantial evidence for a purpose greater than just
display. Although peacocks do go to great lengths to 
attract the opposite sex. Then again, peacocks don't
have huge femoral feathers, nor do they seem to be
highly cursorial creatures....     

> Does flapping keep the effective surface area the
> same? ~:-|

Doesn't that depend on the time interval between wing
beats? 

> Does any living glider do that?

Living gliders can only provide so much information on
the evolution of flight, especially considering the
variations of this strategy in the dissimilar groups
that practice it. Wouldn't incipient flappers be
quickly out-competed by more derived flappers? 

> I rather think of an airplane which adjusts its
> rudders by just a few degrees and keeps them that 
> way to change its angle to the ground. An
> unexperienced pilot would have to play around with
> the rudders to find the optimal solution, but still
> wouldn't do anything repetitive -- and that
> fast --, I think. (But then, planes can't flap in
> the first place...)

Right. Planes are just gliders with a power source.

> Maybe when it doesn't realize that what it's doing
> is novel. :-) (A few proposed examples are: 
> flapping evolved from jumping and fighting in the
> air -- the theropods realized afterwards that the
> more they beat up their enemy, the longer they 
> stayed in the air; 

The problem I see is that when an animal uses an organ
for a new purpose, it usually uses it for a purpose
similar to whatever came before. Legs came from fins,
and wings came from arms....they all revolve around
the need for locomotion. The function is somewhat
different, but the main theme is clear. If the above
example were found to be true, do modern flying birds
imagine a rival bird just ahead taunting them on? The
genes responsible for these behaviors are interlinked,
and would have to be decoupled somehow I'd guess.
There has to be a reason for shifting from one primary
function to another.     

> FUCHSIA --
> the theropods flapped faster and faster and 
> realized afterwards that they had left the water; 

- Which would come as a great shock, and probably
cause the bird to tumble back into the water. The
sudden transition would be confusing, disorienting,
and destabilizing.

> vertical running -- they kept on running after the >
tree had ended. :-)

I like the idea of vertical running, but I'd propose
that whatever they were running after (say a young
pterosaur?) leapt off the trunk and they simply
pursued it. Wouldn't  branches stop the progression up
the tree before it reached the top, too?
  
> Hm... it doesn't just have a fan at the end, unlike
> what the new dromie appears to have, but almost the
> entire tail supports long feathers.

Right, they're just longer at the end than more
proximally.

> Various birds of paradise, paradise whydahs etc.
> have very long tail _feathers_.

Yup, and for what purpose? :^)

> There are still 2 genera or so of long-tailed bats,
> and I wonder why pterosaurs evolved short tails so >
late (but twice).

So, you deny that there is a phenomenon here?
There must be some advantage to having a short tail or
some disadvantage to having a long tail. If there
wasn't, why do these creatures diverge from the
plesiomorphic condition?

> Requires very, very long femora. We have such long
> ones, *Yandangornis* had, but I can't think of 
> others...

Eh? Sorry....don't follow you.

> Sounds possible (indeed the humerus never points
> directly laterally in birds), but wouldn't longer 
> feathers evolve more probably? 
 
Behavior evolves faster than feathers, or it's just
learned. Holding the humerus against the trunk is a
faster fix than growing longer feathers. 

> > I can think of several gliders that have
> > evolved wings or patagia near the CoG. The Draco
> > lizard, and *Sharovipteryx.*
> 
> May be more evidence that bird wings didn't evolve
> for gliding.

Depends on wing position. How could birds evolve a
system like that if the legs were restricted to
fore-aft movement? They would've had to find
alternative ways of supporting their bodies without
having patagia centered near the CoG. 
   Before I end this post, I'd like to ask an
off-topic question. Do the barbs on each rachis
support the bottom of adjacent rachis (rachi rachises
rachae?) in bird feathers? Or do they overlap them?   


Cheers, 
Waylon Rowley


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