Sinosauropteryx and Compsognathus manus

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

I am writing in response to Berislav Krzic's "Feathered Dinosaurs" words
and images at
<http://www.geocities.com/CapeCanaveral/Lab/1638/feathers.html>.

Bravo, Berislav!  The decomposing _Protarchaeopteryx_ image is so
naturalistic, I can practically smell it.  Of course, I've gotten so caught
up with _Sinosauropteryx_ fever that the sight of any feathered Mesozoic
non-avian theropod is enough to make me lose my objectivity, so I urge you
all to judge for yourselves.

Now on to the manus of _Sinosauropteryx prima_.  I've commented on Philip
Currie's description (and projected sketch) of this before, based on
Currie's talk at the 1997 SVP in Chicago.  I feel that it is important for
me to comment on this, because I believe that my post to this list led
directly to an error in Beri's text.

I still stand by my assertion that Currie stated that "the first metacarpal
is quite short," "the first digit is robust," and the ungual phalanx of the
first digit is very large indeed relative to the other digits on the
diminutive hands of this theropod.  But when I stated that the remaining
element of this first digit, the first phalanx, was also short, I was
wrong.  As the January 8 _Nature_ article points out, this element, and the
corresponding ungual, were "relatively large, each being as long as the
radius, and thicker than the shafts and the distal ends of either the
radius or the ulna.  This unusual character seems to have been partially
developed in at least phalanx I-1 of _Compsognathus_."  Again, the ungual
and first phalanx of digit one are not exceptionally long, but are long in
comparison to other elements.  Until an actual illustration of the manus is
published, there will continue to be some confusion.  My original letter
was sent prior to the _Nature_ article.

The _Nature_ article proposes a tridactyl manus for _Compsognathus
longipes_, in opposition to John Ostrom's assessment in his thorough
_Osteology of *Compsognathus longipes* Wagner_ paper, but this condition is
not altogether unexpected, as it had been predicted by Gregory S. Paul and
Jacques Gauthier.  As Paul and Gauthier have pointed out, the manual
elements of the _Compsognathus_ fossils are disarticulated and scattered,
and one would expect this theropod to have had three fingers, as its
closest relatives did.

To his credit, Ostrom recognized the controversy in labeling and
articulating the manual bones, and included von Heune's labels for
comparison with his own on the camera lucida drawing of the Solnhofen
specimen on page 79 of his paper.  Close inspection reveals that -- as the
authors of the _Nature_ article suggest -- von Heune was most likely
correct in assigning the longer element of the first finger to the first
phalanx, rather than the metacarpal.  In other words, what Ostrom calls R
Mtc 1 should be labeled R I-1, as per von Heune.  This makes more sense,
because the camera lucida drawing reveals that this bone articulates with
the impression of the ungual, R I-2, and the wrist bone should not
articulate with the claw bone!  One would expect _Compsognathus_ to have
had a hand which resembled that of its recently discovered clade-mate,
_Sinosauropteryx_, even though the proportions differ somewhat.  Obviously,
Ostrom did not have the luxury of studying the Chinese theropod before the
1978 publication of his paper.

I have a related question for the list: to what extent would the gastralia
of the compsognathids restrict the flexion of the spine?  Could the back
bend a lot, a little, or not at all?  The _Nature_ article states:

"The median gastralia cross to form the interconnected 'zig-zag' pattern
characteristic of all theropods and primitive birds like _Archaeopteryx_
and _Confuciusornis_."

Ralph Miller III <gbabcock@best.com>

"One lump or two?"
"I'll take two."