This is really exciting, and a great question.
To me, there are really two contrasting pieces if evidence. Primarily, you have the Kulindadromeus find which suggests feathers as a basal trait if dinosauria (or twice evolved if you are of that camp). On the flip side you have the abundance of dinosaur fossils found without evidence of feathers.
My best educated guess would say that most theropods probably had feather integument in varying degrees. I would also hypothesize that feathers were less useful to the large bodied herbivorous dinosaurs for the most part, and they would either be lost early in those clades, or retained as a juvenile only trait.
Unfortunately those are just slightly evidenced conjecture. As far as Im aware, we do not have the evidence to point strongly either way.
- Nickolas A. Brand
given that feathery integument could be a synapomorphy for Dinosauria, which other clades of dinosaurs you think could be found with preserved fibrous/feather integument? I mean, except those that already "proved" to have them, like ornithomimosaurs, tyrannosauroids, deinonychosaurs etc. Is there a possibility of finding such integument in dinosaurs like _Torvosaurus_, _Coelophysis_ or even _Iguanodon_ and _Pachycephalosaurus_? Thank you in advance, Tom