A feathered dinosaur is any species of dinosaur possessing feathers. While this includes all species of birds, there is a hypothesis that many, if not all non-avian dinosaur species also possessed feathers in some shape or form.

However, Professor Paul Barrett of the British Natural History Museum says on the matter, "We have really strong evidence that animals like the duck-billed dinosaurs, horned dinosaurs and armoured dinosaurs did not have feathers because we have lots of skin impressions of these animals that clearly show they had scaly coverings. We also have zero evidence of any feather like structures in the long-necked dinosaurs, the sauropodomorphs."

It has been suggested that feathers had originally evolved for the purposes of thermal insulation, as remains their purpose in the down feathers of infant birds today, prior to their eventual modification in birds into structures that support flight.

Since scientific research began on dinosaurs in the early 1800s, they were generally believed to be closely related to modern reptiles, such as lizards. The word dinosaur itself, coined in 1842 by paleontologist Richard Owen, comes from the Greek for 'fearsome lizard'. This view began to shift during the so-called dinosaur renaissance in scientific research in the late 1960s, and by the mid-1990s significant evidence had emerged that dinosaurs were much more closely related to birds, which descended directly from the theropod group of dinosaurs and are themselves a subgroup within the Dinosauria.

Knowledge of the origin of feathers developed as new fossils were discovered throughout the 2000s and 2010s and as technology enabled scientists to study fossils more closely. Among non-avian dinosaurs, feathers or feather-like integument have been discovered in dozens of genera via direct and indirect fossil evidence. Although the vast majority of feather discoveries have been in coelurosaurian theropods, feather-like integument has also been discovered in at least three ornithischians, suggesting that feathers may have been present on the last common ancestor of the Ornithoscelida, a dinosaur group including both theropods and ornithischians. It is possible that feathers first developed in even earlier archosaurs, in light of the discovery of highly feather-like pycnofibers in pterosaurs. Crocodilians also possess beta keratin similar to those of birds, which suggests that they evolved from common ancestral genes.

 

Note:   The above text is excerpted from the Wikipedia article Feathered dinosaur, which has been released under the GNU Free Documentation License.