PARAPHYLY IN STEGOSAURUS

[Tetanurae <Tetanurae@aol.com>]

Here's a weird idea....  I am wondering about the polarity of a few characters
in Stegosaurus ungulatus.  Is there a skull, or any skull material known for
this species?  Are there any parascapular spines preserved?  Are the
preacetabular process of the illia flaring like in other stegosaurs or closer
to parallel as in Stegosaurus stenops and Huayangosaurus?

The reason I ask is that all of these would be very useful in deciphering the
relationships of derived stegosaurs.  Stegosaurus stenops appears to be
closest to Wuerhosaurus because they have very thin plates in two rows that
alternate.  The plates also appear to be fairly wide fore to aft, compared to
the taller more numerous flame shaped plates of other stegosaurs.

Lexovisaurus appears to be the sister group to this clade because it has a
very wide ischiadic peduncle on the illium, and a rod like preacetabular
process like the aforementioned stegosaurs.  Since there are 2 1/2 plates
preserved it is impossible to know if they were paired or not.  It does
however have big parascapular spines.

So anyways...  my idea is that the genus Stegosaurus may be paraphyletic, with
Stegosaurus stenops (probably should be called Diracodon stenops) closer to
Wuerhosaurus (and possibly Monkonosaurus too), and Stegosaurus ungulatus as
the sister taxon to that.  Lexovisaurus also appears to be very close to
Stegosaurus and is probably the outgroup of the aforementioned taxa.  The
snout called Paranthodon africanus appears to be more similar to Diracodon
than any other stegosaurs, but it's relationship vis a vis Lexovisaurus and
other headless wonders can't be known...

So, yes, I would be very interested in comments on this idea, as well as the
answers to the questions at the beginning of the post.

Peter Buchholz
Tetanurae@aol.com