WE DON’T know for sure if Tyrannosaurus rex had feathers, but it's a safe guess that it did. This may sound surprising: the mighty T. rex was covered in feathers? The idea is comical enough to some to be the subject of a viral image (above, via saurian.blogspot.co.uk). The evidence for this is based on a few spectacular fossils of other tyrannosaurs - close cousins of T. rex.
Two different tyrannosaurs, the human-sized Dilong and the nearly T.rex-sized Yutyrannus, have been found covered in feathers. The fossils of these tyrannosaurs come from China. They are among thousands of dinosaur fossils there that have been found sheathed in a coat of feathers.
The first feathered dinosaurs were found about 20 years ago and today these are some of the most famous dinosaur fossils in the world, as well as the clearest proof that birds evolved from dinosaurs.
The feathered dinosaurs are important because they are uniquely preserved. Usually only bones, teeth, shells, and other hard parts fossilise. It is very rare for softer parts like skin, muscles, and feathers to turn into fossils. If you've ever seen a deer carcass on the side of the road you'll know why: the soft parts start to decay really fast, as they are eaten by bugs and destroyed by the weather.
But in a few spectacular cases soft parts can become fossilised. The feathered dinosaurs are one example. Their feathers, as well as skin and in some cases muscles and internal organs, were preserved because these animals were quickly buried by a volcano.
So we know that two of the closest relatives of T. rex had feathers. We also know that many other species of carnivorous dinosaurs also had feathers, based on other specimens from China. These include dromaeosaurids, therizinosauroids, oviraptorosaurs, and compsognathids.
So feathers were normal for carnivorous dinosaurs, and the close relatives (and hence ancestors) of T. rex possessed them. This doesn't necessarily mean that T. rex itself had feathers, but it's a very reasonable guess. It also doesn't mean that T. rex had a full array of colourful feathers like a bird. It certainly didn't have wings, as there is no way it could have flown.
It might have just sported a reduced smattering of feathers, the same way that an elephant has a very thin coat of hair. An elephant is probably a good example in this case: too much hair and it would overheat because of its huge body size. For T. rex, too many feathers might have put it at similar risk.
Maybe someday we can test this hypothesis by finding a rare fossil of T. rex that was fossilised in that set of perfect conditions for preserving feathers.
- Steve Brusatte, resident palaeontologist