I am rooting for the flying fish! But this is also a perfect example of why something may not be able to evolve further when faced with an animal that has existing domination of that micro ecology.
The winged birds are much more agile. They dominate the air and thus prevent better flight capabilities in the fish. If the fish started flying higher and further, the birds would have an easy meal. The evolutionary pressure on the fish seems to be to not fly further and higher. If the birds were wiped out the fish would most likely evolve to fly better and thus evolve far better muscular systems and wings. Maybe ending up bat like but aquatic. Cool :-)
So if pterosaurs dominated the skies and birds were evolving flight capability, it may have been a very similar scenario; that the birds “didn’t want to” fly better until there were no more pterosaurs.