Re: pteros have lift-off

[David Peters <davidpeters@att.net>]

> 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