I guess with that we can toss out all thoughts of pterosaurs trying to
reduce drag through streamlining.
Something else seems to be more important -- at least to this one.
I would further add that tossing out "all thoughts" of streamlining is
a bit extreme, not only because it ignores the relative importance of
streamlining different parts of the animal, but also because such a
statement suggests that a streamlined animal must be adapted to lower
drag at every turn possible.
In reality, drag needs to be reduced "enough" (which varies from case
to case), and only rarely to an absolute minimum. Pterosaurs have big
draggy heads (most of them), but probably had very efficient airfoils.
Even with a dewlap, the L/D ratio could have been quite good. There is
always the possibility that Pterorhynchus had adaptations elsewhere in
its morphology to increase lift to compensate for the draggy dewlap, as
well.
I guess the message I'm trying to send is that considering the
importance of drag without considering the efficiency of lift
production can lead to poor conclusions.