[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Re: Caudipteryx: My Reflections on the Postcranium [was: Details on....]



Mickey_Mortimer (Mickey_Mortimer@email.msn.com) wrote:

<Although what you describe would be more evidence to support my
hypothesis C. dongi is synonymous with C. zoui, I cannot see it
in the figures.  The last six or so chevrons of NGMC 97-9-A are
shallow and craniocaudally elongate with a ventral blade.  The
chevrons of BPM 0001 look extremely similar.  The last few
easily visible (directly below and above the crack in the
matrix) are blade-like and craniocaudally elongate.  I cannot
see the distal chevrons of IVPP V 12430 in enough detail to
determine their morphology.  No Caudipteryx specimen shows the
morphology of Nomingia where distal chevrons are rectangular
with very little or no ventral expansion.>

  Mayhap a detailed description of the tails is in order. I can
demonstrate what I mean better if I had this illustrated (which
I've been working on), but let me try it first orally (well,
manually).

  The chevrons in the C. zoui type and paratype, and C. dongi
type, and the two new specimens (C. zoui? and C. sp.?) vary in
the place that the chevrons become shallow and longer
craniocaudally (chevrons are roughly trapezoidal to
subrectangular), occuring in the distal half in the IVPP V12430,
BPM 0001, and NGMC 97-9-A, and proximal to the mid-point in NGMC
97-4-A and IVPP V12344. The proximal chevrons are much longer
(over 6 times their proximal craniocaudal length) in IVPP
V12344, NGMC 97-9-A, BPM 0001 (unknown in IVPP V12430), but much
shorter in NGMC 97-4-A. The craniocaudal length of the chevrons
increases more proximally in the tail in BPM 0001, IVPP V12430,
and *Nomingia*, less so in NGMC 97-4-A and IVPP V12344, and
least so in NGMC 97-9-A. The distal chevrons are skid-like in
NGMC 97-4-A and 97-9-A, but are deeper and robust, and form a
partitioned blade in all other specimens. That of *Nomingia* is
more derived in the nearly mutual contact of chevrons in the
distal half, rather than the distal fifth, as in IVPP V12430 and
V12430, and BPM 0001. Thus the tails of the type and paratype of
*Caudipteryx zoui* seem more plesiomorphic in regard to the
"pseudopygostyle" than in all other referred specimens. *C.
dongi* can be distinguished from the type and paratype on the
basis of the relative size of the sternum, manal proportions,
and tail morphology, which more closely approximates that of
*Nomingia* than does *C. zoui.* Playing devil's advocate, I can
see why Zhou and Wang separated IVPP V12344 from *C. zoui,* but
the identifications of the latest two specimens is much more
suspect, due to the incomplete sternals and poor pectoral
preservation in IVPP V12430. Similarly, I am wary of the sternal
proportions as being indicative of relationship, since this is
notoriously variable in some birds (ratites come to mind) within
the species, and preservation depends on the degree of
ossification of the base cartilage. Sternals may even degrade
with age, becoming more brittle and preservation dependance less
certain, even in a lagerstätten like Sihetun or Chaomidianzi.

<Interesting observation.  I just figured they were scars for
articulation of the sacral ribs.>

  Lateral side, not medial.

<Apparently they are on the lateral surface though.  I disagree
that they are present in Microvenator however (at least not
noticible in Makovicky and Sues 1998 figure or the photo at the
AMNH website).>

  They are present in the AMNH photo, peer closely. I had this
blown up to verify what I was looking at, surprised as I was. I
was all for dumping the idea of a "Caudipteridae."

  more later,

=====
Jaime A. Headden

  Aaaaaaaaaaaaaaaaaaaahhhhhhhhhhhhhhhhhhr-gen-ti-na
  Where the Wind Comes Sweeping Down the Pampas!!!!

__________________________________________________
Do You Yahoo!?
Get personalized email addresses from Yahoo! Mail - only $35 
a year!  http://personal.mail.yahoo.com/