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Re: pteros have lift-off




As I have said over and over again, launch is at about 25 to 35 degrees. 25 degrees is lower than 30 degrees. 35 degrees is higher. The animals can adjust the launch angle at will, though larger animals do tend to go out at a lower angle. I suggest that birds of any species are not necessarily a particularly close analogy for terrestrial pterosaur launch since they do it so differently.

So at a launch angle of 25-35º ground effect is employed for a very short duration in pterosaurs? As opposed to airplanes and big birds, which stay within a downbeat of the ground or water until sufficient speed is attained...



Looks like: 1) crouch simultaneous with wing unfolding and upbeat. 2) hindlimb extension simultaneous with first downbeat. No surprises. Probably common to most birds.

And mostly irrelevant to pterosaurs.

Maybe not. That's what we're trying to understand here. Pterosaurs came from a lineage of hind limb leapers.

So, I'm gathering from the video that a large amount of thrust is generated by the wings along with thrust from the hind limbs. Which seemingly relieves the hindlimbs of a large amount of duty -- which was a major concern of yours.

Of who's ? Birds generate as much as roughly 90% of their launch power with the hindlimbs, depending upon species.

Mike Habib. As a courtesy, Jim, you were cc'd. Since pterosaurs came from a lineage of hind limb leapers, there was a time when pterosaurs, or their immediate ancestors, ALSO generated as much as roughly 90% of their launch power with the hindlimbs. If that gradually decreased as evolution changed things, a change in launch mode, such as you suggest, has to be documentable.


What if someone found trackway evidence for a bipedal pterosaur or two? Would that change your view?

And this is incompatible with small and large pterosaurs because...?

It's not at all incompatible with pterosaurs -- it just has nothing much to do with them.

I think the jury is still out. You present a good case, but it depends on quadrupedality in all pterosaurs, something that has not yet been documented. This is pertinent because they came from bipedal ancestors.


Final question: how much angle do you figure at the carpus to create your Z fold in the forelimb?


JimC




David Peters davidpeters@att.net