Left: The so-called catapult mechanism in pterosaurs. Right: The actual design of a pterosaur hand (in this case Anhanguera/Santandactylus). Note there can be no pinching of the extensor tendon beneath the weight of the pterosaur. The metacarpals were not configured on the dorsal (in flight) or lateral (on the ground) side of metacarpal 4 in ANY pterosaur specimen. They were anterior whether you follow Bennett's (2008) interpretation or mine.