The common ancestor of all dinosaurs may have even been a feathered species. We don’t know for sure, because we can’t study that ancestor directly, but it’s an inference based on an observation: so many small dinosaurs from Liaoning that are well preserved—the bounty of meat-eating theropods like Sinosauropteryx but also pint-size plant-eaters like Psittacosaurus—are found coated in some type of integument. Either these various dinosaurs evolved their feathers separately, which is unlikely, or they inherited them from a deep ancestor.
