Steve Doolittle wrote about the demise of the pterosaurs:
"Which brings me to this question: If the dinosaurs evolved into birds, why
did they do that when that ecological niche was already filled by the
pterosaurs? Because they could do the flying thing better? Maybe the birds
filled a niche that the pterosaurs couldn't?"
Well, I don't think the first of the birds competed with the big pterosaurs. I don't believe that competition with birds drove the great, soaring pteoraurs such as Pteranodons to extinction. It is probable that Pteranodon and friends couldn't do well in a very wide range of environvents, due to their aeriation style. So when the winds started blowind a little harder, they were chained to the coastal cliffs and caverns and starved. Soaring birds evolved after this great dying. The birds living simultaneously with pterosaurs wouldn't have had kids capable of competing well enough with the great dragons of the air. This is because adaptive evolution consists of accumulating unidirectional bits of little, undirected and aimless, random change. The offspring of the ancient birds could be obly a little different from their parents not adapted to soaring, and so they couldn't compete with the pterosaurs. Soaring birds didn't evolve, because the creatures giving birth to the intermediate forms were never born.
"So what the hell happened to the little pterosaurs? If they were being
"phased out" by the dominance of the birds, why didn't they fill another
niche? I mean, the dinosaurs did it."
I think feathers proved to be better than leathery wings for flapping flying. The ability to walk well on land may also have played some role.
As for why the pterosaurs didin't fill another nice, the only and obious explanation coming to my mind is that no immediate offspring of a little pterosaur could compete successfully with creatures of other niches. Empty niches probably weren't filled, because the pterosaurs trying to live differently from their parents did even worse.
Well, as it is said, that's my two cents.