Ah, the fearsome T. rex! Mighty carnivore of the cretaceous! Able to scarf down hapless cavemen in a single bite! Possibly snuggly soft and covered with fluff! Yeah, if there's one thing that utterly fails to make giant carnivorous dinosaurs more badass, it's the fact that they (or their relatives) were likely covered in soft, downy feathers.
Paleopoultryists from the Chinese Academy of Sciences in Beijing have unearthed three new tyrannoid fossils, not T. rex but an entirely new (and more primitive) species that they've named Yutyrannus huali, which means "beautiful feathered tyrant" in a combination of Latin and Mandarin. All grown up at nine yards long and 1.5 tons, one of these dinos would only been about a fifth the size of a T. rex, but Yutyrannus is by far the largest dinosaur ever to be found with direct evidence of featheryness.
It would be fun to suppose that feathers mean that Yutyrannus was capable of flight, but it's far more likely that it was using feathers for insulation instead. Tests of oxygen isotope ratios in the dino's teeth showed that it was living in an environment that averaged just 50 degrees Fahrenheit, which is a bit on the chilly side, so a feathery coat would certainly make sense. It's also possible that the feathers were used for sexual displays, camouflage, or all of these things.
So, since an ancestor of the T. rex definitely had feathers, does that make it any more likely that the legendary lizard king itself also sported some fancy plumage? Yes, maybe. Larger animals have less of a need for insulation (since their volume increases faster than their surface area does), but it's entirely possible that T. rex had feathers when it was young, or perhaps it had feathers on some of its body if not everywhere. Either way, don't let cuddlyness fool you. As paleontologist Tom Holtz of the University of Maryland puts it: "underneath the fluff, it's still the same gigantic crushing teeth and powerful jaws and softball-sized eyes staring at you. [The downy feathers] might make it a little more amusing, but only until the point right before it tears you to shreds." So it's one of those laughing and crying things then, is it? Good times.