BY NOW, I think most people are getting comfortable with the idea of feathered dinosaurs. Like many of us, I grew up with the idea of dinosaurs as giant, drab-coloured reptilian beasts.
This is how dinosaurs were portrayed in most books I remember as a child. But now, open up the pages of most dinosaur books, or flip on most dinosaur TV documentaries, and colourful feathered dinosaurs are the norm.
New fossil discoveries over the past two decades tell us that many carnivorous dinosaurs had feathers. There are more than ten species of meat-eating dinosaurs that have been found covered in feathery coats. Most of these come from the fossil-rich farmlands of northeastern China.
These ‘feathered dinosaurs’ include dromaeosaurids, therizinosaurs, oviraptorosaurs, and even tyrannosaurs.
We know for certain that famous dinosaurs like Velociraptor and Ornithomimus had feathers. And one of the most recent discoveries - the skeleton of the dog-sized carnivore Sciurumimus from the Late Jurassic of Germany - tells us that even very primitive theropods had feathers.
So it is clear: most, if not all, meat-eating dinosaurs were sheathed in feathers. Some had big feathers with vanes, just like the ‘quill pen’ type-feathers of living birds. Others had simpler feathers, like the down feathers of living birds, which are used to keep warm. And some species had simple hair-like strands. But regardless of what the feathers looked like, all or most theropods had them.
But what about other kinds of dinosaurs? Ornithischians - the group that includes Triceratops - for example?
Believe it or not, we now know that some ornithischians had feathers as well. Two incredible fossil discoveries prove this. First, there is a well-preserved specimen of the small horned dinosaur Psittacosaurus (an early cousin of Triceratops) with a series of hair-like bristles running down the tail. Second, there is a beautiful specimen of the small, fast-running Tianyulong (a heterodontosaurid ornithischian) with similar bristles covering the neck, back and tail.
These bristles aren't exactly the same as the feathers of living birds. In fact, they look quite different. They are more like the quills of a porcupine: long, perhaps hollow, structures that stand up straight, forming something that would have looked like a Mohawk.
They did not have vanes, or barbs, or barbules, or the other components of the characteristic ‘quill pen’ feathers of living birds. They were not used for flight, but were more likely used for display: to intimidate rivals, impress mates, or differentiate one species from another.
But although these bristles are different from the feathers of living birds, scientists are confident that they are essentially the same type of structure. In other words, they are comprised of the same material and are controlled by the same basic genes. In more technical terminology, they are 'homologous' to feathers.
The bristle-like structures of ornithischians are probably primitive versions of feathers. The earliest dinosaurs probably evolved simple feathers like this for display or to regulate body temperature, and later they were modified into more elaborate structures that were useful for an entirely new purpose: flight.
- Steve Brusatte, resident palaeontologist
- Illustration by Todd Marshall