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Re: Spinosaur synonymy

Waylon Rowley (whte_rbt_obj@yahoo.com) wrote:

<Some list members have suggested that Cristatusaurus
lapparenti, Baryonyx walkeri, and Suchomimus tenerensis could
all be the same genus. Well, I have a short list of apomorphies
for diagnosing the latter 2.>

  I'm going to rework (but not revise) Waylon's list so that it
cound be interpreted in a cladistic manner ... here goes and
keep all boos inside the car doors:

 1. Scapulocoracoid union, peg-in-notch: absent, 0; present, 1.
 2. Sacral centra, strongly constricted mediolaterally: absent,
0; present, 1. [first I would ask that this be quantified,
restricted compared to _what_?]
 3. Caudal centra, strongly constricted mediolaterally: absent,
0; present, 1. [first I would ask that this be quantified,
restricted compared to _what_?]
 4. Nasals, form: separate, 0; fused, 1.
 5. Nasals, sagittal crest: absent, 0; present, 1;
 6. Nasals, cruciate caudal projection between orbits: absent,
0; present, 1.
 7. Lachrymal projection: absent, 0; horn-like, 1; small and
knob-like, 2.
 8. Fibula, medial fossa, depth: shallow, 0; very deep, 1.
[again, compared to what?]
 9. Premaxillae and nasals, meet below external nares: present,
0; absent, 1.
 10. Dorsal, sacral, and [anterior] caudal neural spines,
expanded dorsally into a "sail": absent, 0; present, 1. [one
might desire a neural spine to centra comparison....]

 Other characters given are autopomorphous for a single species
(or OTU), and thus not diagnostic or relevant to relationship;
additionally, I've added a few that will work with
*Cristatusaurus* inclusion, and *Irritator*, to give an idea of
the distribution here; hardly a concise list (I have one
elsewhere, and Sereno et al. have done extensive work as well).

 11. Teeth, serrated: present, 0; absent, 1.
 12. Premaxilla, dorsal crest extent: absent, dorsal margin
smooth, or rugose, 0; forms a shallow plateau, or dorsally flat,
1; extends as a clear "cristate" ridge, 2.

  Outgroup         000000000000
  *Baryonyx*       000111201000
  *Suchomimus*     100111001101
  *Cristatusaurus* ??????????01
  *Irritator*      ???1100?0?12
  *S_maroccanus*   ??????????12
  *S_aegyptiacus*  ?00??????11?

  Ran through PAUP, this tree has 31 MPT's, a Consistency Index
of .8462, a Homoplasy Index of .1538, and a Retention Index of
.7143, with 13 steps each; the concensus tree is an unresolved
polytomy of all taxa, so offering a topology would be useless.
Baryonychinae is monophyletic and exclusive of Spinosaurinae and
the Outgroup in 9 trees, and *Suchomimus* + *Baryonyx* is found
only in 9 trees, but of these, only three have the topology of
(Cristatu (Sucho + Bary)), 7 have *Suchomimus* +
*Cristatusaurus*, and 4 have *Baryonyx* + *Cristatusaurus* as
mutual closest taxa. Baryonychinae including *Cristatusaurus*
occurs in 13 trees. The variability of *Criustatusaurus'*
position (it becomes a shifter in a few, and the best tree finds
Sucho as a Spinosaurine based on the presence of a "sail." 

<Does anyone have a more reliable (or otherwise different) set
of apomorphies for these 3 animals? Thanks!>

Clarification of the distribution of these characters and the
distribution of others may clarify relationships -- or I could
run a modified version of Sereno et al (1998)'s tree and see if
I can place *Cristatusaurus*.... Some possibly diagnostic
characters include the distribution and arrangement of premax
teeth, a max/premax diastema, spacing of maxillary/dentary
teeth, form of interdental plates, largest tooth position, form
of longitudinal dental striae (wrinkles), proportion of pinching
of premax/max, form or extent of rosette, both dentary and
premax, and even max... These can be determined for both
*Cristatusaurus* (to some degree, anyway) and *Spinosaurus
maroccanus.* Maybe later I'll try to code them, but for now....

Jaime A. Headden

  Where the Wind Comes Sweeping Down the Pampas!!!!

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