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RE: South Dakota fossil yields new dinosaur species

Lucas Panzarin (heby@libero.it) wrote:

<The new pachies seems to share with Pachycephalosaurus wyomingensis and
Stygimoloch (but also with the unnamed "Sandy" specimen) a cluster of hornlets
on the nasal, plus 2 series of various spikes on the rear of the squamosal, and
a very prominent jugal boss...>

  In all due fairness, *Sygimoloch* (and it's apparent synonym *Stenotholus*)
are only known from the dome (frontoparietal), surrounded peripheral bones, and
portions of the occipital complex including the huge horn-encrusted squamosals.
No nasal bones showing rostral borns. As for the jugal boss, this exists in all
"rootward" pachycephalosaurs, more especially so it seems in
"homalocephalid"-grade taxa than in fully-domed "stegoceratine"-grade taxa,
including clusters of nodes on the surface.

<what is really weird is the presence of completely open supratempotal
fenestrae, reminiscent of those oh Homalocephale...a very strange combination
of advanced and primitive character.>

  Some of the spikes associated with *Stygimoloch* and therefore "Sandy" may
belong to this taxon instead.

<Very young pachycephalosaurs have no dome and open supratemporal fenestrae,
but the long spikes are an adult feature, so the new skull could'nt be a
juvenil. Another point: this is the first pachycephalosaur to sport knobs and
hornlet over the dome (Prenocephale, Colepiocephale, Hansuessia,
Pachyphalosaurus, Stygimoloch, Stegoceras, but also Homalocephale or
Goyocephale have smooth skull dome, or at most a wrinkled surface)..>

  Well, the dorsal surface of the frontoparietal in these was very ornamented,
but not thickened or expanded: in *Homalocephale,* *Wannanosaurus*, and
*Goyocephale* the dorsal surface is covered in "bumps", texturizing the skull.
There is no dome in these taxa, and so the elaboration in this skull of the
dorsal surface into spikes would simply seem to be enlarging these midline
rugosities or "bumps" into spikes; not too much of a difference. All
pachycephalosaurs, especially the "homalocephalid"-grade ones, have nodes on
the rear parietal and squamosals; in "homalocephalids" at least, these nodes
are more pointed and spike like, especially in *Goyocephale*.

  When the press-release stated that Bakker intimated researchers tore up their
cladograms, I was mildly amused, since this doesn't really change anything in a
cladogram. They just need to look deeper, sample more, not be mammalogists.


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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