Size and Weight:
For the past couple of decades, paleontologists have been speculating about whether or not large tyrannosaurs like Tyrannosaurus Rex and Albertosaurus sported feathers--if not as adults, then at some stage during their youth or adolescence. Now, the recent discovery in China of the largest feathered tyrannosaur yet identified, Yutyrannus, is sure to rekindle the debate about whether T. Rex and its ilk were green, scaly and reptilian or soft and downy, like a giant baby duck.
The early Cretaceous Yutyrannus, which weighed in the neighborhood of one or two tons, isn't the first feathered tyrannosaur ever discovered; that honor belongs to the much smaller Dilong, a 25-pound Yutyrannus contemporary. It's also important to keep in mind that we have solid evidence for feathered theropods that didn't happen to be tyrannosaurs, some of which reached equally respectable sizes, if not quite in Yutyrannus' weight class.
One important question now confronting paleontologists is, why did tyrannosaurs like Yutyrannus evolve feathers in the first place? Flight was out of the question for a 2,000-pound theropod, so the most likely explanation involves some combination of sexual selection (perhaps brightly feathered Yutyrannus males were more attractive to females) and insulation (feathers, like hair, help to regulate the metabolism of warm-blooded organisms, which theropods almost certainly were).