From Nature:
“I’d go so far as to say that all dinosaurs had some sort of genetic trait that made it easy for their skin to sprout filaments, quills and even feathers,” says Barrett. ”But with scales so common throughout the family tree, they still look like they are the ancestral condition.”
The findings provide “a valuable reality check for all of us who have been enthusiastic about suggesting dinosaurs were primitively feathered”, says Richard Butler, a palaeontologist at the University of Birmingham, UK, who was not associated with the study.
Butler, however, goes on to say that we don’t really know because there are just not enough skin impressions from the earliest period yet.
So far, we mainly know that the therapod (bird-like) dinosaur were mostly feathery and the sauropod (lizard-like) dinosaurs were mostly scaly. It certainly would be interesting if feathers turned out to be common in the earliest state. We’d add that one to the “Earlier than thought” list.