I’m not going to say much about this since Ed Yong has an excellent write-up, but a new feathered dinosaur has been discovered, called Tianyulong. As you can see in this image of the fossil, it was bristling with a fuzz of thin fibers — proto-feathers.

(Click for larger image)
a, Main slab of the holotype (STMN 26-3). b, Broken slab. The scale bar in b refers also to a. c, Close-up of skull and mandible. d, Interpretive drawing of skull and mandible. e, Close-up of dentition. Abbreviations: a, angular; aof, antorbital fossa; ca, caudal vertebrae; cv, cervical vertebrae; d, dentary; dv, dorsal vertebrae; emf, external mandibular fenestra; en, external naris; f, femur; h, humerus; isc, ischium; j, jugal; l, lacrimal; m, maxilla; n, nasal; pd, predentary; pf, prefrontal; pm, premaxilla; po, postorbital; pub, pubis; q, quadrate; qj, quadratojugal; scaco, scapulocoracoid; sa, surangular; tf, tibia and fibula.

There are a couple of noteworthy features in this creature. One is apparent: feathers just didn’t bloom suddenly in evolution, but appeared in steps. This animal has ‘feathers’ that don’t branch like those of modern birds, but instead form more of a furry coat than a set of flat blades.

The other cool thing is that this is an ornithischian dinosaur; most of the other dinosaurs that have been discovered to have feathers were saurischian. What that means might be made more clear by this diagram:

It implies that just maybe the last common ancestor of the saurischia and ornithischia were also covered with proto-feathers, which means that feathers may be a primitive state in this lineage.

Zheng X-T, You H-L, Xu X, Dong Z-M (2009) An Early Cretaceous heterodontosaurid dinosaur with filamentous integumentary structures. Nature 458:333-336.