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Re: pterosaur femora sprawl

True. But no pterosaurs walked, bipedally or quadrupedally, with a horizontal backbone. Elevate the spine at the shoulders and voila. MPUM 6009 is still derived in many regards, so it is the most basal _known_ pterosaur.

You'll need to give more detail on how you are so certain that no pterosaurs walked with a horizontal vert. column. Of course, the more vertical stance does not greatly affect quad launch, which is how we got into the stance issue in the first place.

re: Odd adaptation for bipedalism:
Don't forget the albatross and the hummingbird (comparatively small legs).
Case closed? : )

Hummingbirds can barely walk; I wouldn't consider them a good example of bipedalism.

Albatrosses have short hindlimbs, but they follow the typical avian scaling trend in structural strength: the hindlimbs, despite being small, are very strong. In fact, the femur of an albatross can sustain more load than the humerus, even though the humerus is obviously the larger element and involved in the primary mode of locomotion. However, the hindlimbs are the primary launch module, and the forelimbs are not. So, in fact, albatrosses vs. pterosaurs supports the quad stance and quad launch for pterosaurs.



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