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Re: pterosaur femora sprawl



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