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Sinosauropteryx protofeathers



Pharris Nicholas J wrote:

> IIRC, the Chinese researchers claim that the second, larger specimen of
> _Sinosauropteryx_ has much larger feathers than the first, and that these
> feathers are "foliated" (which I assume to mean they are ovoid and show a
> branching structure like feather barbs or leaf veins).  That would be a
> thing to see!
>
> Has Currie or Ostrom had anything to say on this specimen?  Have they even
> been allowed access to it?

Yes, indeed they have had access, and Currie has had much to say.  Ostrom et
al. (also known as the "dream team") had examined _Sinosauropteryx_ quite a
while ago, and were unable to reach a consensus regarding the "feathers."
This should come as no surprise, as among the party was Larry Martin, who
disagrees with the prevailing hypothesis that birds are descended from
theropod dinosaurs.

Mr. Martin later collaborated with the Oregon State zoologist team (John Ruben
et al.) in presentations proffering the hypothesis that the fibers represented
the remnants of internal fibers supporting a midline frill, such as one sees
in extant aquatic reptiles (sea snakes and marine iguanas, for example).  This
hypothesis met with much criticism, and has been proven invalid through the
direct study of the fossils by Philip J. Currie and the Chinese
paleontologists; considerations of the morphology of the _Sinosauropteryx_
filaments versus internal fiber frill support anatomy of extant animals, and
the comparative anatomy of compsognathids versus aquatic animals likewise
prove the hypothesis false.  Ruben et al.'s characterization of the
"crocodilian" respiratory system of _Sinosauropteryx_ is likewise unsupported
by the fossils, but the team will continue to present their controversial
views at future symposia, as they choose.

Philip J. Currie has had ongoing contact with the Chinese paleontologists and
their prized _Sinosauropteryx_ fossils (as well as the _Protarchaeopteryx_ and
_Caudipteryx_ specimens).  From the very start, he has stated publicly his
opinion that some of the filaments of the former branch and that they may have
a rachis, although he has conceded that the precise anatomy is unclear, due to
the fibers being piled up atop one another.

In the Currie and Padian's 1997 _Encyclopedia of Dinosaurs_, under the title,
"_Feathered" Dinosaurs_, Currie writes: "The integumentary structures were
simpler than true feathers, and each seems to be composed of a central rachis
and branching barbs but lacks the aerodynamic quality of avian feathers."

Last October, he responded to my question regarding the protofeather anatomy
of _Sinosauropteryx prima_ as follows:

"My observations suggest that there are two sizes of filaments in the
protofeathers.  The larger, more dispersed ones are hollow (figured in an SEM
photo in one of Ji's Chinese papers), and the longer, thinner ones are
probably branches off the larger ones.  Hope to have a more detailed
description available soon."

This exchange was provided as part of the Dinosaur Interplanetary Gazette Dino
Dish forum.  My question can be viewed at
<www.InsideTheWeb.com/messageboard/mbs.cgi?acct=mb29768>.  My post, "Chinese
Dinosaur Questions," dated October 09, 1998 can be found about 1/5 up from the
bottom of this long page of posts.  If you have difficulty with this URL,
access the Dinosaur Interplanetary Gazette at
<www.dinosaur.org/frontpage.html>, and click on "Message Board!  Ask
Questions.  Get Answers!"

The _Nature_ paper (June 25, 1998) compares the filaments to the plumules
(downy feathers) of extant birds, but points out that the fossil filaments are
coarser than the fur fibers of comparably sized mammals, so I would take this
to mean that the fibers weren't as delicate or fluffy as modern avian down
feathers.  Currie's sketch of the fiber structures (as seen at the 1997 SVP
meeting, Chicago) looked to me like a number of fibers fused together at the
base (where the short rachis would be located); the mention of "branching
structures" emanating from a "rachis" must not be taken to mean that the fiber
organization (if accurately interpreted) approaches the look of an ostrich
plume.  It is difficult to assess the precise meaning of the Chinese authors
(Ji and Ji) in their application of the word "foliated"  in the paper you
cite, due to the language problem ( a problem amply evident in the garbled
English translation).

Not everyone agrees with the view that the fibers branch from a rachis, but it
appears to me that the majority of those who have studied the specimens
firsthand seem willing to accept the interpretation that the fossil filaments
represent the remnants of external integumentary fibers of some kind which may
be referred to as "protofeathers" (if not "feathers" proper).  Gregory S.
Paul, writing about the 1997 SVP meeting, reported that Mary B. Schweitzer
presented images of vulture head feather fibers which apparently show no
branching whatsoever (similar to the preserved fibers she studied on a
specimen of _Mononykus_), although other bird feathers invariably feature a
rachis (shaft) and at least some barbs either proximally (at the base) or
distally (at the tips).  Hence, because it would be awkward to refer to a
modern vulture's filament as a "protofeather" rather than a feather, one could
make a case for calling the _Sinosauropteryx_ fibers "feathers," as long as we
understand what the term means.  It would certainly be more accurate than
calling the features "fur," as the latter term applies only to mammals.

If you haven't seen it already, the July 1998 _National Geographic_ has some
nice photographs of _Sinosauropteryx_, including close-ups of the putative
eggs, the mammal jaw inclusion, and the fibers themselves (see p. 83, top!).
This issue covers _Protarchaeopteryx_ and the fabulous _Caudipteryx_, too.
Some background on feathered dinosaurs can be accessed at
<www.nationalgeographic.com/dinorama/birdlike.html>; magazine back issues can
also be ordered through the site.

And, for your information, there are now four specimens of _Sinosauropteryx
prima_ known, although they have not all been described in journals just yet.

Ralph Miller   <gbabcock@best.com>