Proto-feathers (basically hair) were basal to dinosaurs + pterosaurs, we have evidence for feathers on some dinosaurs (micro raptor had iridescent black feathers), fuzz on others (Psittacosaurus has long “quills” on its backend), and scales on others (Carnotosaurus, Diplodocus, large portion of T-Rex)
The idea right now is that the smaller ones probably had feathers, bigger ones had scales, unless they’re from China, then everything has feathers