Bending strength of several major bones in Quetzalcoatlus and two other azhdarchid pterosaurs.

The ‘avian expectation’ indicates the expected strength in bending for each element if pterosaurs followed the structural scaling of birds. Relative Failure Force is the ratio of cantilever failure force, in bending, divided by body weight. Note that the proximal forelimb of the sampled pterosaurs is much stronger than expected from the avian trend, but that the femur of Quetzalcoatlus is only 30% as strong in bending as would be expected for a bird of its size.