A useful and up to date image showing the coverings of theropod dinosaurs.
Feathers are epidermal growths that form the distinctive outer covering, or plumage, on Coelurosauria dinosaurs. They are considered the most complex integumentary structures found in vertebrates, and indeed a premier example of a complex evolutionary novelty.
Feathers are often discussed to be found mostly on Coelurosauria dinosaurs which is the clade containing all theropod dinosaurs more closely related to birds than to carnosaurs.[1] It's also debated if big dinosaurs like Tyrannosaurus rex had feathers or not because the 1st found remains of a Tyrannosauridae relative named Yutyrannus had feathers which is still open to debate on if all of them had feathers or not. Even now scientists can answer if they believe all dinosaurs at first had feathers but that feathers are evolutionary throughout the linage of generations of dinosaurs[2]. Fossil remains of pterosaurs have been found with a feather-like covering known as pycnofibers, which points to a possible shared trait in their common ancestor.