I had forgotten to mention something. I haven't actually checked out the June issue of National Geographic yet. I'll tell you if it answers any of your questions.
The dinosaurs were said to be all killed in a massive flood, but there were dinosaurs that lived underwater, so this wouldn't apply to them. Add to that, there were smaller dinosaurs that actually lived on into present-day Earth. So why were they singled out? It seems there's some pieces of the puzzle we haven't unveiled just yet.