Accurately distinguishing between which taxa are dinosaurs and which are birds is a necessary first step in showing that birds and dinosaurs are not connected.
Tyrannosaurs, Compsognathus, Ornitholestes, Therizinosaur
Paraves (flying and flightless), Alvarezsaurids (secondarily flightless), Oviraptors (secondarily flightless)
I will deal later with the traits that help us determine how to distinguish between dinosaurs and birds.
Of course the primary trait is pennaceous feathers. Another significant trait is the orientation of the pubic bones.
Here are some of the traits that distinguish dinosaurs* from birds:
Pennaceous feathers, pubic bone orientation, sternum, patagium and propatagium.
Those are a few of the traits. These traits listed are very significant.
* by "dinosaurs" I am referring to saurischian dinosaurs since the dino to bird theory claims that birds descended from saurischian dinosaurs