Re: vaulting pterosaur launch, questions

[Erik Boehm <erikboehm07@yahoo.com>]

> > Sorry to switch focus from pterosaurs to birds, but
> how do you picture 
> > _Archaeopteryx_ getting itself airborne from terra
> firma?  By leaping 
> > from a standstill off the ground?

I would be very interested in knowing what sort of environment pterosaurs and 
archaeopteryx's ancestors evolved in.
I don't know how the later ones started flying (birds today will both do a 
running takeoff, or just leap into the air), but I highly doubt the first ones 
to begin to fly just leapt into the air.


Going away from paleontology, and into aviation:
Birds always take off into the wind, a 9 mph wind would be enough to make up 
the difference between the 2 m/s running speed, and 6 m/s stall speed.

The local weather and terrain can dramatically effect how easy it is to fly. 
Perhaps this Tree vs Ground debate is overestimating the requirements for 
flight, and ignoring the situations where I personally find it to be easiest to 
fly.

Certainly, windy coastal dunes or cliffs would allow very easy flight without 
the need to run anywhere near flying speed, or flap. It is at coastal dunes 
that humans were first able to reliable practice flight- first at Kitty Hawk 
with the Wright brothers, and then southern california beaches with 
hang-gliding.
Early hang-gliders had horrendous glide ratios (like 4:1), and pretty bad sink 
rates- but could still soar coastal dunes with sufficient wind. If I recall, 
that was about the estimated glide ratio of Microraptor (which occurs after 
Archaeopteryx, so I'm assuming the Dromeosaur linage is secondarily flightless).

I don't know how bats evolved, and the numerous arboreal gliding animals do 
seem to strongly hint that perhaps an arboreal origin is likely. How would an 
animal transition from gliding flight between trees, to powered flight?
I wonder if there were any forests that went right up to the beach with coastal 
cliffs/dunes when and where pterosaurs/bats/birds evolved.
Such an arboreal glider should be able to fly in the ridge lift, and could then 
perhaps develop further flight adaptations.

I learned to fly hanggliders at coastal dunes, flying there is super easy - I 
can run nowhere near fast enough to get off the ground with my glider, doesn't 
stop me from flying.

If you are interested in seeing just how "easy" flight is at coastal dunes, you 
might want to check out these videos on youtube showing real examples of 
completely unpowered coastal soaring in aircraft with sink rates and glide 
ratios far worse than the majority of birds:

http://video.google.ca/videoplay?docid=-2214328225178239829

http://www.youtube.com/watch?v=fCSCE2NN0YI

http://www.youtube.com/watch?v=-qA6pN1aeZ4



More videos if any of you care to see them:

http://www.youtube.com/watch?v=pQLDq2JFlx8

http://www.youtube.com/watch?v=ahR05bIy_9s

And the following videos have more efficient Glider's, that also have higher 
stall speeds:

http://www.youtube.com/watch?v=md6HaYAFJWQ&;

http://video.google.ca/videoplay?docid=6054797528719720590