Re: pterosaur femora sprawl

[Michael Habib <mhabib5@jhmi.edu>]

> The most likely gait, as you'll see, is the only gait that permits 
> pterosaurs to easily change from quad to biped, to balance over the 
> toes, to open their wings and take off. Now, if they rebounded into 
> the air from some sort of momentary spring-loaded crouch that you are 
> envisioning, that I want to see.

I was more wondering what factors led you to choose that gait in the 
first place, rather than the effects you would expect it to have.  
Changing from biped to quad might be interesting or useful, but that 
doesn't mean it must have been the gait that was used.  And, as Jim 
already pointed out, you have the order of launch reversed: flying 
vertebrates leap first, then engage the wings (even if they launch 
bipedally like birds).  A gait that places more weight on the hind 
limbs does not make launch any more efficient for pterosaurs, though it 
doesn't really constrain them either - the quad takeoff still works 
just fine (the animals just shift weight more noticeably onto the 
forelimbs during the crouch and unload).  The key here is that opening 
the wings before leaving the ground isn't actually very helpful, so 
being able to balance on the hindlimbs and open the wings is of limited 
importance.  That's not to say that pterosaurs were incapable of doing 
so, but merely that it would be unrelated to launch ability.  Might be 
useful for sunning one's wings, though.

Cheers,

--Mike


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