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Re: Feathers on Bloody Everything

Let's not forget that there are a couple dozen good swatches of dinosaur
skin impressions, known from all "major groups" of dinosaurs (i.e.
ankylosaurs, stegosaurs, duckbills, ceratopids, sauropods, theropods,
etc.).  Prior to the last couple of years, the only known Mesozoic animal
whose skeleton was as much non-avian dinosaur as bird and whose fossils
revealed definitive evidence of feathers was _Archaeopteryx_.  The
extensively "mummified" duckbill specimens and the generous _Carnotaurus_
impressions offer most compelling proof that not all (non-avian) dinosaurs
sported feathers throughout their lives, not even all theropods.  Agreed?

Now, when we talk about the discovery of the three described non-avian
feathered theropod dinosaur species -- _Sinosauropteryx_ (a
"protofeathered" dinosaur, if you prefer), _Protarchaeopteryx_, and
_Caudipteryx_ -- and a certain feathered therizinosaur who shall remain
nameless until published -- this is very welcome and marvelous news, and,
again, suggests that many theropods wore some kind of insulating
integument.  But it doesn't quite reveal the precise nature of tubercles or
feathers worn by the many theropods for which the integument is unknown,
much less do these finds address the question of what hatchling dinosaurs
of these and other clades might have worn.  The tentative statement that a
15-foot-long therizinosaurid has been found with preserved "feathery"
integumentary structures represents the first hint of good evidence for an
insulating fiber integument in a _somewhat_ larger non-avian dinosaur,
which is significant.  But the unknowns are still considerable.

Before we can assume that feathers "belong" on other dinosaur groups
(fluffy ankylosaurs, anyone?), we must consider the many superficial
variations that exist today among "much more closely related animals".  And
remember, for all it's worth, Mark Norell's statement that _Tyrannosaurus
rex_ is more closely related to extant birds than to other members of the
dinosaur "clan."  "Dinosauria" may represent a valid taxonomic and
phylogenetic entity, but we must examine the striking diversity in other
aspects of dinosaur anatomy before painting them all with the same brush
(so to speak).  There were certainly more dinosaurs with feathers than the
fossils have thus far revealed, but there were certainly dinosaurs with
tubercles and osteoderms, too.  On the plus side, I haven't yet seen a
dinosaur encyclopedia that puts "feathers on bloody everything."

-- Ralph Miller III     gbabcock@best.com