Proteins were discovered in fossilized feathers which were previously believed to only be present in modern animals.
The question of whether Fujianvenator, with its curious mixture of skeletal features, should be classified as a bird or a dinosaur is still in debate.
Unknown dinosaur species from the Cretaceous period discovered in Morocco, near Casablanca.
Researchers described the newly discovered creature as similar to Edward Scissorhands because of its long claws.
"Here, we have good evidence for a smaller mammal preying on a larger dinosaur, which is not something we would have guessed without this fossil," Mallon added.
"Dinosaurs nearly always outsized their mammal contemporaries, so traditional belief has been that their interactions were unilateral - the bigger dinosaurs always ate the smaller mammals."
The placoid scales are not seen on speedier shark species, as those species have scales with spaced ridges.