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Re: pteros have lift-off

David Peters wrote:

......... There aren't any known pterosaurs with roughly a 3x longer wing.

Yes, there are, in relation to torso length. Not absolute length. We're modeling here. So everything is to scale with a torso length as a more or less common unit.

Wing length relative to torso length doesn't really have a huge impact on ground clearance issues (aside from the absolute wing length). And I think you've overestimated - I can't think of any species with a full 3x relative wingspan compared to Quetzalcoatlus sp. By that metric, there should be something out there with half the torso length, but a 27.5 foot wingspan. That's pretty extreme.

Unfortunately, that's really not where I'm looking for clearance. Let's move the video back a few frames and see if there is this thing called wing clearance much earlier in the launch -- closer to where the hands are still only inches to feet above the ground and rising quickly.

Well, if the hands were at the ground, and then they are rising - where is a ground clearance issue going to arise? It could only possibly happen if the wing finger was moved into flight position immediately, which it wouldn't be. In fact, taking the extreme case - we can simply model the wing finger as staying fully folded until the top of the upstroke. It probably doesn't actually do that, because opening a bit earlier saves energy by utilizing inertial unfolding, but every pterosaur I've looked at so far *could* do that if wanted. So that's the most straight-forward sequence (and one that works just fine, simply not the most optimal): leap, unfold at the top of the upstroke, downstroke.

You mentioned the animal has .72 seconds to bring the wing to the beginning of the first downstroke. I'm wondering what the wing finger is doing at .1, .2, .3, and .4 seconds into the launch.

It's still completely folded until about 0.25, more than likely. But, if it wants, our leaping pterosaur can simply leave the wing finger folded up until the 0.7 mark when it begins to downstroke. It makes the initial upstroke faster anyway.



Michael Habib, M.S. PhD. Candidate Center for Functional Anatomy and Evolution Johns Hopkins School of Medicine 1830 E. Monument Street Baltimore, MD 21205 (443) 280 0181 habib@jhmi.edu