Well according to many people birds today are dinosaurs. (they are indisputably members of "Dinosauria")
But as with pretty much everything, there would have been a long period where they were on the border of being birds. Categories in biology always have blurry boundaries. And those boundaries will of course adjust as we get more fossils and other information.
But as with pretty much everything, there would have been a long period where they were on the border of being birds. Categories in biology always have blurry boundaries. And those boundaries will of course adjust as we get more fossils and other information.