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Re: Lumping Spinosauridae Redux



Tim Williams (twilliams_alpha@hotmail.com_ wrote:

<That reminds me... Oliver Rauhut raised the specter that the type
material for _Spinosaurus aegyptiacus_ might be a chimera, with the jaw
material and vertebrae coming from separate animals.  If this is the case,
which element will bear the name _Spinosaurus_?>

  I think a lectotype would need to be selective if, and only if, it could
be demonsrated that the material did not all come from one kind of animal.
It doesn't help that there are very crappy caudal remains of other
spinosaurids that limit comparative research, as those in *Baryonyx* are
not well-illustrated or scrappy, those in *Suchomimus* are incomplete, and
that in *Spinosaurus* ... well ... some have different opinions about
their nature. However, since I consider the weight of the evidence as
favoring the holotype is of a single animal, I would disfavor selecting
_any_ other type. That the material is lost would mean a neotype would
have to be selected from material in collections, which are largely teeth
and fragments of jaw. So it is likely any usch material would be cranial
than vertebral, if chosen.

  I beleive this absolutely will be answered in a different way when Josh
Smith gets his historical work, on Stromer's work and Markgraf's notes on
the collection itself, actually published. I don't know the full details,
but Stromer says [tanslated, I don't want to type the German right now]:
"the collector Markgraf excavated a number of closely associated remains
of a large theropod, namely the two mandibular rami without the posterior
ends, with a few teeth _in situ_, a ?left angular, a little piece of the
upper jaw, over a dozen individual teeth or tooth crowns, two cervical,
seven dorsal, two and a half sacral, and one anterior caudal vertebrae,
many incomplete ribs, and lateral gastralia." (pg. 3).

  The color of the material was consistent, as was their preservation, so
it is not likely they were associated post burial. Possible pre-burial
association may have occured, and part of Rauhut's explanation if I recall
correctly was to question the association of the caudal vertebra to the
holotype, but as I think other dinosaurs have proven out, some theropods
_do_ have "hollow" caudal centra, as Stromer indicates this vertebra is
hollow: "On it an artificial hole is present, which leads into an
irregular hole in the middle of the centrum, which probably likewise was
artificial, but its production was probably assisted on account of the
especially porous spongiosa." (pg. 22). The portion about the "porous
spongiosa" leads me to suspect the internal structure was camellate.
*Fukuiraptor* and sauropods have camellate caudals, among others, as did
the caudal vertebra *Walgettosuchus,* but the morphology of this material
is not sauropodan, and it is not certainly ornithischian as has been
implied by Rauhut (in his thesis, at least), especially given its
camellate internal structure. Rauhut suggested the caudal was "too large"
for the dorsals, but this is not true, as the caudal centrum alone is only
half the length of that of the last dorsal identified, suggesting it is
from a little further back than the base of the tail [yes, if and only if
it belongs to the same animal as the dorsals]. I do not see any convincing
evidence that *Spinosaurus* is a chimaera. Other dinosaurs in the Baharija
with the same spines as *Spinosaurus,* but with a different skull, and a
croc-jawed theropod without the spines, might go a long way to proving
Rauhut's theory. Spinosauridae has priority over Baryonychidae if they are
considered to be synonymous, whether or not *Spinosaurus* is a nomen
dubium.

  Cheers,

=====
Jaime A. Headden

  Little steps are often the hardest to take.  We are too used to making leaps 
in the face of adversity, that a simple skip is so hard to do.  We should all 
learn to walk soft, walk small, see the world around us rather than zoom by it.

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)


                
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