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I wholeheartedly agree with George, and I certainly hope Norell qualifies his statements by saying ornithischians and sauropodomorphs most likely had bristle-like protofeathers (and that they probably did not cover the whole body). If not, he is going to give some people the false impression that they had vaned feathers like maniraptors and birds (i.e. birds sensu Kinman) and that they were first developed for body insulation (which I strongly doubt). And it is certainly very disturbing to see Chinese scientists calling pterosaurs "feathered" if all they had were hairlike bristles.
As for the sauropod embryos (or ornithischian embryos for that matter), I believe the first "bristles" would have been along the backbone and tail. If my "protofeathers evolved on the tail first" hypothesis is correct, they may well first appear on the tail and then spread up the spine during ontogeny.
I think this hypothesis may be supported by the bristle-tailed psittacosaur. If tail bristles evolved first, then they may well have been the last to be lost as dinosaurs got bigger. It is therefore no surprise to me that dinosaurs had considerable portions of the bodies lacking such protofeathers. Even once exapted for brooding, only the posterior parts of the adult would *need* to be covered with brooding bristles. Perhaps only in advanced coelurosaurs did they spread to arms and eventually become exapted for aerodynamic functions.
---- Cheers, Ken Kinman
P.S. As for Longisquama, its paravaned parafeathers may well be homologous to protofeathers, but they are pretty clearly convergent on real vaned feathers found in Class Aves (sensu lato).
Dinogeorge wrote:
For some time now I've suspected (and argued) that all dinosaurs had feathers of some kind--perhaps not like those of modern birds but certainly homologous keratinous dermal structures. These might occur quite far down the archosaur clade and could well be homologous with pterosaur "hairs" and even Longisquama "wings." Nice to know that there might actually be some hard evidence for these.

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