This confuses me greatly. According to a new paper published in Zitteliana by Mike Habib, pterosaurs launched themselves into the skies quadrapedally with a "leap-frog" motion. I cannot, for the life of me, envision this. I remember seeing this concept as a poster session at last year's SVP, but there, as here, there are no figures showing exactly how this would work. What we really need is an animation. Can somebody explain this one to me?
Ridiculously awesome update: In the comments, Christopher pointed to the launch sequence of a vampire bat. I'm sold, and it would probably work for rhamphorhynchoids, too.