Page "Dromaeosauridae" Paragraph 12

The first known dromaeosaur with definitive evidence of feathers was Sinornithosaurus, reported from China by Xu et al.

in 1999.

Many other dromaeosaurid fossils have been found with feathers covering their bodies, some with fully developed feathered wings.

Microraptor even shows evidence of a second pair of wings on the hind legs.

While direct feather impressions are only possible in fine-grained sediments, some fossils found in coarser rocks show evidence of feathers by the presence of quill knobs, the attachment points for wing feathers possessed by some birds.

The dromaeosaurids Rahonavis and Velociraptor have both been found with quill knobs, showing that these forms had feathers despite no impressions having been found.

In light of this, it is most likely that even the larger ground-dwelling dromaeosaurids bore feathers, since even flightless birds today retain most of their plumage, and relatively large dromaeosaurids, like Velociraptor, are known to have retained pennaceous feathers.

Though some scientists had suggested that the larger dromaeosaurids lost some or all of their insulatory covering, the discovery of feathers in Velociraptor specimens has been cited as evidence that all members of the family retained feathers.