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Sinosauropteryx prima



Dino-playmates,

I finally got around to reading the Pei-ji Chen, Zhi-ming Dong,
and Shuo-nan Zhen paper on the integument of _Sinosauropteryx prima_,
in _Nature_. 

In short, I found their paper both refreshingly objective, and
shamefully incomplete.


Their paper was a conservatively-interpreted view of
the main points that we have been discussing here for the last
year or so.  I think that their conservative approach to the
particular issue of integument was wise, considering the very
preliminary data on these structures, incomplete data on the
structures, and <unfortunately, still-> poorly-illustrated structures
that have been published to date (in my opinion, the best
published photos of _S. prima_ STILL remain those found
in the magazine _Audubon_ (March-April, 1997)).  As a result,
Pei-ji Chen et al.'s original, authoritative, primary
defining paper on the subject has illustrations that are
at best, only of cursory note, and they still take a back seat to
those found in the _Audubon_ spread.

Having said this, however, I found the paper very well written,
and full of "new-ish" data that hasn't been emphasized
on this mailing list in any great detail (at least as far as I know).
For the benefit of many of you who don't have access to
_Nature_, I present here some quoted tid-bits from
Pei-ji Chen et. al's paper (Chen et al. in quotes; non-quoted,
or <> stuff is my wording):

1) "Diagnosis.- Compsognathid with longest tail known for
any theropod (64 caudals); skull 15 % longer than femur,
and humerus+radius only 30% length of femur+tibia, in contrast
with Compsognathus where sk<u>ll is same length as femur,
and humerus+radius is 40% femur+tibia; within Compsognathidae,
forelimb length (compared to femur length) is shorter in
_Sinosauropteryx_ (61%-65% than it is in Compsognathus (90-99%);
in contrast with all other theropods, ungual phalanx II-2 is longer
than the radius; haemal spines simple and spatulate, whereas
those of Compsognathus taper distally"

2)  Fossil horizon:  The Yixian Formation is mostly *not*
sedimentary. The fossiliferous horizon in question is one of the
sparse sedimentary layers near the base, and is 60 meters thick.

3)  "_Sinosauropteryx is comparable in size and morphology to
known specimens of Compsognathus from Germany and France. The smaller
Chinese specimen is 0.68 meters long from snout to end of tail...
femur length of 53.22 mm.....second larger specimen has a femur
length of 86.4 mm...."

4) Diagnosis of Compsognathidae: "unserrated premaxillary teeth,
and serrated maxillary teeth; manual phalanx I-1 shaft diameter
is greater than that of the radius); fan-shaped neural spines
on the dorsal vertebrae; limited anterior expansion of the pubic
boot and a prominent obturator process of the ischium."

5) "Both specimens of _Sinosauropteryx_ have 10 cervical and 13
dorsal vertebrae."

6)  Shape of distal ends of the 13 dorsal ribs indicate a
"suggestion of cartilaginous sternum".

7) Two eggs (37 X 26 mm) present in the body cavity near
pelvic girdle. (similar dual-oviduct egg-laying style as is seen
in Varricchio et al.'s description of _Troodon_?).
So we <probably> know the sex of one of the
two specimens (unless the eggs were eaten, but the authors dismiss
this based on the position of the eggs in the body cavity).

8) Integument:  "The orientation and frequently sinuous lines of
the integumentary structures suggest they were soft and pliable,
and semi-independant of each other.  They frequently cross each
other, and are tangled in some areas.  There is an apparent
tendency for the integumentary structures to clump along the
tail of the smaller specimen, but this is an artefact of the
splitting plane....<There are> integumentary structures on the
left side of the body.....those <integumentary structures>
associated with the right ulna are 14 mm long...<the integumentary
structures> are piled so thick that we have been unable to isolate
a single one for examination.  Comparison with birds from the
same locality shows that the same problem exists with identifying
individual feathers (other than flight feathers) and components
of feathers in avian specimens."

9) Possible grammatical error?: (left-bottom of page 152) "Finally,
the aerodynamical capabilities of bird feathers are not
comprised <compromised??> by the previous evolution of less
complex protofeathers that had some other function, such as
insulation."


Since I have interests in the hyoid apparatus of birds and other
higher vertebrates, I had earlier noticed a structure that
resembled a hyal element directly underneath the dentary (in the
_Audubon_ photos, in particular).
I read through the Chen et al. paper to find any discription of what
there was of this stucture, but sadly, nothing was mentioned.
Perhaps it isn't a hyal element?

But, all in all, the paper is a good general discription of the
specimen, with a correctly cursory and cautious interpretation of it's
integument. I was somewhat annoyed, however, that the authors
didn't bother to include some imaging specialists in as authors,
who could have *easily* conducted the necessary SEM, TEM, and
IR spectral imaging on a sacrificed piece of integument. 
Sacrificing a small fragment of the specimen is a necessary evil,
and *must* be done in order to resolve the issue. Biochem analysis
would be the next step after that.  A multi-disciplinary
"dream team", comprised of paleontologists, ornithologists,
X-ray imaging specialists, multi-spectral imaging specialists,
electron microscope imaging specialists, and biochemists, is
the only route to take with such a unique group of fossil
specimens. As hard as it is for some people to understand,
relected-light imaging is not going to resolve
the issue.  And as much as I respect Phil Currie and his
magnifying lense and his glossies, for some reason that just
doesn't seem rigorous enough to me.

Oh, well...maybe the up-coming Sinopter' papers will cut
through the integument haze a bit more.


Refs:

Chen, Pei-ji, Zhi-ming Dong, and Shuo-nan Zhen. 1998.
An exceptionally well-preserved theropod dinosaur from the
Yixian Formation of China. _Nature_, vol. 391,
(Jan. 8, 1998):147-152.


Morell, V. 1997. The origin of birds: the dinosaur debate.
_Audubon_ March-April, 1997:37-45.


Varricchio, D.J., F. Jackson, J.J. Borkowski, and J.R. Horner.
1997. Nest and egg clutches of the dinosaur _Troodon formosus_
and the evolution of avian reproductive traits. _Nature_ vol. 385,
Jan. 16, 1997:247-250.


Un-flapingly, yours,
                   <pb>



--
                 Phil Bigelow
                 bh162@scn.org