Davide Bonnadonna We tend to think of feathers as one of the defining features of birds. But in recent years, it's become apparent that the lineage of dinosaurs that gave rise to birds (the Theropods) had feathers millions of years before anything remotely bird-like existed. Just last week, feathers were also found on a dinosaur outside the theropod lineage, raising questions about what made the theropods special (aside from, well, all sorts of cool dinosaur species). Previous attempts to detect any global trends in bird-like traits among the theropods haven't come up with anything definitive.