The study suggests that the dinosaurs went through a huge range of shapes and sizes over these years. And those species that decreased their body mass, survived and became birds. This evolution helped the dinosaurs maintain their presence, albeit in another much smaller form, and allowed them to continue exploiting new ecological niches throughout their evolution.
It has been only more than two decades that the idea that birds evolved from dinosaurs have entered mainstream acceptance. This can be largely attributed to the movie "Jurassic Park" which broached the theory to the public and garnered massive acceptance. Although some of the facts in the movie turned out to be wrong, the dinosaur to bird evolution theory still remains.
There have also been fossils discovered that suggests that some dinosaurs have feathers just like their current cousins. And there are also some, like the Microraptor had wings.
