Re: My Phylogeny: Growing Science...

["Jaime A. Headden" <qilongia@yahoo.com>]

Mickey Mortimer (Mickey_Mortimer11@msn.com) wrote:

<Caenagnathids seem to have some remnants of interdental plates.>

  Caenagnathids most certainly do not have interdental plates. And frankly, 
neither do
troodontids. I have no idea where the latter came from, but I feel that I am 
partially responsible
in that I suggest to Mickey somewhere that the medial alveolar wall of the 
dentary in
*Caenagnathasia* was analogous to the condition of interdental plates, as in 
Troodontids. Well,
neither have interdental plates (see Currie, 1987, in _JVP_, and Currie et al. 
1994 {cited 1993),
in _Canadian Journal of Earth Sciences_). Personal observation suggests that 
not even
*Caudipteryx* or *Microvenator* had interdental plates, and just have the 
alveolar pits left over
from reduction of the lingual (medial) alveolar wall of the dentary. This 
condition is less
advanced in troodontids, but nonetheless present. There are walls between 
individual teeth in both
the maxilla and dentary of *Troodon* (Currie, 1987, 1989), as seen in 
*Saurornithoides junior*
(Barsbold, 1974) and *Byronosaurus* (Norell et al., 2000). There are no plates 
preserved, and the
medial wall is much higher than normal for theropods _with_ the plates (pers. 
obs.) indicating the
compensation for the plate loss was related [and also to the severe packing of 
anterior teeth in
the jaws]. The condition in *Pelecanimimus* is unknown.

<Yes, but it's crushed and broken.  I don't think any useful information can be 
seen, but Jaime's
drawn a reconstruction.  I'm skeptical of his drawing to say the least...>

  Considering I pointed out the various regions of the skull to Mickey, and 
only he has seen the
recon he's referring to outside of my house, this is rather priviledged data. 
But I'm not worried,
and I can send my reconstruction with a scan of the actual elements it was 
derived from if anyone
asks. I would enjoy discussion. However, there is an element that is absolutely 
the prootic and
laterosphenoid portion of the endocranial wall, in lateral view, and portions 
of the
basioccipital, that allow some information to be derived visually. Only 
personal examination can
tell for certain.

David Marjanovic (david.marjanovic@gmx.at) wrote:

<<Do caenagnathoids really have the derived condition?>>

and Mickey replied:

<I have them coded as being primitive, but this was probably from a data 
matrix.>

  Probably. No complete braincase is known for caenagnathids (as described 
anyway). However,
oviraptorids, *Caudipteryx* (unknown in *Avimimus*) and *Erlikosaurus* all have 
a neat little row
of the two exits for the fifth cranial nerve (V^1 and V^2,3), the seventh, and 
the dorsal tympanic
fenestra. It is therefore parsimonious to assume that caenagnathids and 
*Caenagnathasia* have the
condition as well. Code caenagnathids as - until data can be recovered to 
verify or falsify my
hypothesis.

David wrote:

<<18 -- Do we know *Avimimus* has no interdental plates?>>

<Only the premaxillae and dentary tip have been found with "dentigerous" 
margins. The lack of
teeth is associated with the lack of unfused interdental plates as far as I 
know. But it has been
recently suggested Avimimus had premaxillary teeth, which could complicate the 
issue.>

  Again, the word as translated from Russian, _zubov_, refers to teeth as well 
as anything
toothlike, and Barsbold has used the same word in connection with oviraptorids. 
Until someone
shows you an actual tooth in these, the actual premaxilla/maxilla (another 
point Mickey and I
disagree on), which is denticulated (_zubovishchnikaya_), bears about 6--7 
denticulated points and
the crenels between them are trinagular and are not likely to be eroded bone 
(they are also
regularly shaped), and this is apparent what Kurzanov meant when he wrote in 
1985 that the
premaxilla bore about 4 teeth (the Russian word, which I have available, used 
was _zubovoy_).
Apparently, a new *Avimimus* specimen recovered from the Nemegt and reported in 
2000 at SVP in
Mexico City has "teeth" and I am quite curious as to these. Beleive it or not, 
it would make
better sense to me if it did, considering the basal form of the animal relative 
to a
oviraptorosaur paradigm, which I consider more likely than the alvarezsaur or 
paravian one, based
on my own observation. I have no stock held in this argument, though.

<The furcula of Protarchaeopteryx may also be broken (Padian et al., 2001), so 
I'm not sure how it
should be coded.>

  The element, illsutrated in _Mesozoic Vertebrate Life_, is strongly sigmoid 
and appears to have
broken at the midline. It appears to have half of a U-shaped furcula, more 
curvaceous than in
*Archaeopteryx*.


=====
Jaime A. Headden

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

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