Over the last 20 years quite a bit of evidence has accumulated indicating that at least some dinosaurs were feathered, much of it in the form of beautiful fossils from China. Up until now all the feathery dinos have been members of the carnivorous theropods, but this new paper by Godefroit et al (2014) extends that fluffiness in its description of a herbivorous dinosaur, Kulindadromeus zabakialicus. (The full paper is behind a paywall but the BBC offers a good general summary.)
It's now generally accepted that birds evolved from a theropod lineage (Michael Benton discusses the evolutionary changes that this entailed, here), although there is still debate around the origins of things like wings, feathers, and when birds/dinos first took to the air. Most people are probably familiar with at least the name of Archeopteryx, but since 1994 those Chinese fossils have shown us that many more theropods were feathered, and that feathers evolved well before the first bird-like creatures took to the air. Godefroit & his colleagues comment that
fully birdlike feathers orginated within Theropoda at least 50 million years before Archaeopteryx.
and there's even discussion around whether the fearsome T.rex may have been feathery/fuzzy.
But Kulindadromeus wasn't a theropod - it was a 'neornithischian' - an early member of the 'bird-hipped' dinosaurs, a group that includes Stegosaurus and Triceratops. (This nomenclature can get a bit confusing, especially when you consider that birds evolved from 'saurischian', or 'lizard-hipped' dinos.) And while it didn't have the sort of feathers that we're familiar with today, it did have a range of other structures in addition to the usual scales:
monofilaments around the head and the thorax, and more complex featherlike structures around the humerus [upper forelimb], the femur [thigh], and the tibia [lower leg].
It's early days yet. But if other ornithischians are found with feathers, then then this would raise the possibility that the common ancestor of both dino groups also had some sort of feathery structures on its body, and would support the authors' suggestion that
feathers may thus have been present in the earliest dinosaurs.
In other words, feathers may well be much, much older than we've thought.
P.Godefroit, S.M.Sinitsa, D.Dhouailly, Y.L.Bolotsky, A.V.Sizov, M.E.McNamaram M.J.Benton & P.Spagna (2014) A Jurassic ornithischian dinosaur from Siberia with both feathers and scales. Science 345: 451-455 . doi: 1126/science.1253351