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*Stenopelyx valdensis,* the Earliest Pachy?



Adam Yates wrote:

<Stenopelix still stands as an Early Cretaceous,
European pachycephalosaur. This based on a number of
good postcranial synapomorphies (see Sereno, 1999).
I'm especially impressed with the long rod-like sacral
ribs.>

  I don't like this part of Sereno's cg=haracter list
such that it is supported (all of Pachycephalosauria
including *Stenopelyx* all of three characters: set 4,
characters 4-6 in the supplementary info.

  The first (4. Sacral ribs strap-shaped -- state 1)
merely implies the ribs were flatter. On the one hand,
it could be diagnostic. Functionally, this might imply
greater in lesser compressive resistance and thus act
as shock absorbers. It may be convergently derived.

  The second (5. Scapular blade broad at the distal
end -- state 1) persists in *Psittacosaurus* more than
it does in other ceratpsians, and the state is unknown
in *Chaoyangsaurus* [contra Sereno],
*Archaeoceratops,* *Goyocephale,* or *Homalocephale,*
which are all key taxa in this issue (I've not seen
the *Microcephale* paper yet [Dinos of Mongolia and
Asia volume is out -- yippee!], and if any one would
be able to send it my way, I would be very thankful)
and "Graciliceratops" remains undescribed.

  The third (6. Distal end of preacetabular process
expanded -- state 1) is variable within a lot of
Ornithischia, and the new Carrier and Farmer studies
have put a newer reflection on the functional aspect
of this region. Furthermore, all other
pachycephalosaurs are well-diagnosed to 20 characters
(per Sereno), and all of his Ceratopsia characters are
cranial, as are most sub-group taxa, a case which
complicates matters for *Stenopelyx.*

  The German form is a plesiomorphic taxon, the pelvis
rather more psittacosaur-like than not, and the
hindlimbs further are intermediate in general form
between pachycephalosaurs, psittacosaurs, and some
ornithopodous ornithischians like *Hypsilophodon*,
etc. 
I would say that the link between all Laurasian forms
radiated from Europe into Asia, then into America.
Futhermore, a resurgence from Lauraisia into
Gondwanaland in the earliest Cretaceous would suggest
10 there were possibly well0differentiated
ceratopsians in the Late Jurassic, and 2) that forms
in Australia and less determinate material elsewhere
may have a common origin, rather than being
convergence. The leptoceratopsid ulna from NSW,
Australia may either be from a true most-basal
leptoceratopsid, or a form convergent in Lauriasian
leptoceratopsids [= *Udanoceratops*, *Leptoceratops*]
(quadrupedality may be a factor in the form of the
ulna between the two).

=====
Jaime "James" A. Headden

  Dinosaurs are horrible, terrible creatures! Even the
  fluffy ones, the snuggle-up-at-night-with ones. You think
  they're fun and sweet, but watch out for that stray tail
  spike! Down, gaston, down, boy! No, not on top of Momma!

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