But, in fact, it seems true that dinosaurs died suddenly. Due to this question, we have had a glance on some other consequences of a change gravity. Some cosmological models accept the idea of a change of the gravitational constant G during Univere's history. But I believe there does exist clues which indicate that G has changed. This is an indirect proof.
Clues do exist in astronomy too.
It's plausible that this water disappeared because of a change in gravity in the Solar system. Remember that sea levels were higher during dinosaurs age. With a lighter gravity, it's normal that sea levels are higher. During the dinosaurs age, Gravity was light enough to authorize gigantism. But the bird is goind to glide in the atmosphere more easily too.