Sinosauropteryx at Dinofest

["Ralph Miller III" <gbabcock@best.com>]

If anyone could be called the star of Dinofest '98, it would have to be
_Sinosauropteryx prima_.  So ubiquitous were slides of this animal that
presenters at times projected the fossil image with an apology(!) and one
paleontologist received a round of applause when he stated that he would
not be screening any such slides with his presentation.  This was in the
spirit of fun, however, and I don't think people hold personal grudges
against this fascinating little theropod.

Alan Brush presented "Protofeathers: What are we looking for?"  I cannot
provide his illustrations here, and , hopefully he and other authors will
contribute to the Dinofest volume, which will enable us to absorb these
issues in considerably more depth than is possible in this forum.   Alan
Brush took us through the steps of feather development from a placode, or
feather bud, developing first on the dorsal surface, to a conical tubercle
structure, proceeding via differential growth to produce fibers fibers of
varying length and diameter, which can fuse at the base to form a simple
down feather.  In his view, all forms of feathers originate in a similar
way, and the follicle is the key to understanding the rapid evolution of
feathers.  The branching of feathers is seen as a redundant system.  He
stated that the earliest morphological form of protofeather was probably a
barb-like hollow fiber structure.  Need I point out that this morphology
suggests a similarity to the appearance of the fibers seen on the
_Sinosauropteryx_ specimens?

Philip J. Currie's talk on "Feathered Dinosaurs" reiterated much of what he
had said at last October's SVP meeting.  He began his talk by describing
the _Confuciusornis_ feather impressions from the Liaoning province of
China.  The feather structures appear as a sagittal halo because when the
flesh of the body rots, it takes the rest of the feathers with it.  This
pattern is seen over and over again in the approximately 1,000 Mesozoic
birds recovered from the region.  So the fact that fibers are presumably
missing from the flanks of _Sinosauropteryx_ specimens should come as no
surprise.  None-the-less, examination of the three specimens of the
theropod have revealed that the fibers appear not only along the midline,
but also along the back of the quadrate, the side of the ilium, on the
tibia, humerus, ulna, and between the haemal spines.  As Gregory S. Paul
has pointed out, Currie has determined that the fibers are not contained
within the skin -- as the Oregon State team has claimed -- because the
supposed body outline is merely the work of the Chinese preparators
scratching the structures free from the matrix.

Currie characterizes the fibers as being soft and pliable structures,
bending, twisting, and wrapping over each other.  Fibers scattered across
the area -- but not positively attached to the specimens -- have, upon SEM
study, revealed a hollow morphology.  The Chinese authors of the January 8
_Nature_ article have noted that the attached fibers appear lighter in the
middle, and darker distally, also suggesting hollow architecture.  By his
own admission, Currie's characterization of the fibers as showing branching
is more controversial, but if his observation is correct, then this is even
more suggestive of a common ancestry with avian feathers.

Currie reiterated that the tail of _Sinosauropteryx_ is long, but does not
fit the model for an aquatic animal's tail, and that the stomach contents
-- a lizard in one specimen, a mammal jaw in another -- don't match the
aquatic profile (endorsed by Ruben, Geist, Jones, and Martin) either. 
Bruce Mohn gave a talk specifically refuting the aquatic lifestyle
hypothesis for compsognathids, finding no compelling similarities
whatsoever between the skeletons of compsognathids and known aquatic or
semi-aquatic animals.  

Philip J. Currie (like Gregory S. Paul) disputes the characterization of
the alleged internal anatomy as indicative of a croc-like hepatic piston
lung system, on the basis that the so-called "septum" is a crack infilled
with cement on the cited specimen and the stain may be the residue of a
last meal or any other organ, not necessarily a liver.  He further pointed
out that the soft anatomy (if that's what it is) may have been distorted
and moved within the body cavity after death.  Based on the bird-like
structure of the ribs, gastralia, and sternum, quite similar to those of
_Protarchaeopteryx_ and _Confuciusornis_, Currie expects that the enclosed
anatomy would be bird-like rather than croc-like.  He and Steven F. Perry
allocated a separate talk to a thorough refutation of the croc-style
respiration hypothesis.

John Ruben presented "The Implications of soft tissue preservation in the
compsognathid theropod, _Sinosauropteryx_," which was similar to their SVP
talk last October.  The work was attributed to Ruben, Geist, Jones, and
Martin.  Ruben pointed out that crocs eat terrestrial animals, so that the
presence of terrestrial animal remains in _Sinosauropteryx_ specimens does
not refute their hypothesis.  He claimed that the caudal anatomy _is_
consistent with the anatomy of extant aquatic reptiles, including
alligators.  He reiterated the "body outline" claim (which Currie had
refuted monments before) in support of the fibers being internal to the
skin.

Ruben then showed slides of the dissection of a monitor lizard's tail,
which exhibited a dense, uninterrupted band of collagenous tissue astride
the haemal arches.  In an effort to _simulate_ the effects of decomposition
on this dense strip of tissue, the scientists stripped off the bulk of the
material, leaving only a few proximal, shredded strands atop the arches. 
Having performed this operation, they then photographed the resulting
fibers, which had the fuzzy, frazzled, wool-like appearance which Luis Rey
has noted, and which did not particularly resemble the fibers of the
_Sinosauropteryx_ specimens.  If this analysis is to be taken seriously, I
suggest that the fibers be allowed to decompose naturally, without the
artificial removal of material.

In the question-and-answer period, I asked : if the aquatic frill
hypothesis is correct, then why are the fibers found on the ilium, tibia,
humerus, ulna, and  quadrate?  Larry Martin replied that if you haven't
personally examined the specimens as he has, you might not realize that on
the tail of one of the specimens, the fibers are long and parallel to the
spine, just like the collagen tissues of an aquatic lizard.  If this is
true, and these are not the scratches of a preparator trying to clear the
caudal vertebra from the matrix, then this is indeed puzzling.  He further
stated that some of the fibers are actually within the rib cage of one of
the specimens.  If this is true, then some of the fibers may have moved
post-mortem.  I regret that I didn't ask why many of the fibers are found
_between_ the haemal arches, as this doesn't fit the image of "decomposed
collagen atop the haemal arches" model.

Alan H. Brush remarked that there are preparator's scratches on the
specimens, obscuring the true fiber orientation.  He also stated that some
of the observed morphology could represent not the distal branching of
fibers, but the presence of organisms which attached themselves to the
fibers. 

It was emphasized that the fiber diameters need to be carefully measured,
and that someone like Mary Schweitzer should perform tests on the fibers to
determine whether feather keratin chemistry is present.

Then Dong Zhiming appeared and proclaimed that "A fourth specimen has been
discovered."  He stressed the need for expert preparation this time.  Wow!

-- Ralph Miller III     gbabcock@best.com