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RE: Dilong

John Hunt wrote:

The thing about Dilong is whilst those of us who accept that birds are
dinosaurs may have been expecting the discovery on a tyrannosaur with
feathers, the likes of BAND and megaraptor.com were probably praying that
one would not be found!

Alas, they probably didn't turn a hair. We've known for quite a while now that non-avian theropods had some sort of down-like body covering, including compsognathids, alvarezsaurids and therizinosauroids (as well as dromaeosaurs and oviraptorosaurs, examples of which show true feathers of modern aspect). _Dilong_ takes these 'protofeathers' further down the theropod tree, to the tyrannosauroid clade, close to the base of the Coelurosauria.

The Birds-Are-Not-Dinosaurs crowd (which is not such a 'crowd' any more) has tended to dismiss these down-like appendages as something other than protofeathers - collagen fibers, for example. They will probably claim that that the fuzzy covering of _Dilong_ were nothing like true feathers, and irrelevent to the evolution of birds or the origin of flight - as they have done in the past for _Sinosauropteryx_ &c.

_Dilong_ is not just significant for the presence of protofeathers, but also for what it tells us about tyrannosauroid evolution. For example, the reduction in forelimb length occurred after the diagnostic changes to the tyrannosauroid jaws. To a large degree, _Eotyrannus_ indicated that this was the case (and _Eotyrannus_ was also a fabulous discovery); but _Dilong_ fills in so many more details.