theropod quibbles

[rowe@lepomis.psych.upenn.edu (Mickey Rowe)]

Sorry to distract people from pronunciations for a while, and I
suspect that I'd be better off sending this to
sci.paleontology.dinosaurs.theropods.Tom.Holtz, but what the hey...

I read Sereno et al's paper describing _Afrovenator_ last night, and a
couple of things in it bothered me.  The first was probably just due
to a bit of wording that could have been better, but it might also
have been an indication that theory rather than observation was
driving their description on this one point.  The authors state:

   Unlike _Allosaurus_ and many other theropods, cranial crests and
   rugosities are poorly developed.

A quick look at figure 2A indicates that they found almost nothing of
the top of the skull.  The only way I could salvage their comment was
by accepting that the crests to which they're referring are always
found as processes jutting off of the lacrimal bone, the one skull
bone of which they seem to have discovered the dorsal surface.
Looking through the sources I have at home, that seemed consistent at
least with _Allosaurus_.  Is that what they probably meant?

My second problem seems (to me at least) to represent a bit of
careless scholarship on the part of the authors.  In delineating
theropod phylogenetic relationships, they state:

   Torvosauroids include _Afrovenator_, the Laurasion genera
   _Torvosaurus_, _Eustreptospondylus_, and _Chilantaisaurus_ (13),
   and tentatively the spinosaurids _Spinosaurus_ and _Baryonyx_
   (6,14).

The references in footnote 6 are dated 1915 and 1934, so they clearly
refer to _Spinosaurus_ alone and not to _Baryonyx_.  Reference 14 is
Charig and Milner's chapter in _Dinosaur Systematics_.  Since I
recently read that book, it was fresh enough for me to know that
Charig and Milner aren't cited accurately here.  In fact, if I were
Charig or Milner, I'd be angered by the above statement.  From the
conclusions in Charig and Milner, you find the most direct disavowal
you could possibly expect to find of the above position:

      The individual characters found in _Baryonyx_ (Fig. 9.7), some
   of them unique, and its particular combination of characters,
   indicate unequivocally that it cannot be assigned to any known
   family of theropods; more specifically it is not a spinosaurid.  We
   therefore believe that we were justified in placing it in a new
   theropod family of its own (Baryonichidae Charig and Milner, 1986).

Sereno et al may disagree with Charig and Milner, but if they do, then
I think it was incumbent upon them to say so at least in the footnote.
Better yet, if they want to disagree, they should state why.  My
impression (based admittedly on little evidence) is that Charig and
Milner's interpretations aren't popular, but that's not an excuse.  To
cite that chapter as Sereno et al did, is *at best* misleading since
it appears to indicate that Charig and Milner placed _Baryonix_ in
Spinosauridae.

While I'm here, let me also clear up something that may have confused
some of you.  Tom Holtz recently replied to a couple of questions that
many of you never saw.  The reason you didn't see them is that the
person who sent in the questions had an address that got partially
mangled in the Reply-To: address, causing many of your mailer-daemons
to choke on it and spit it back at me.  I'm attemptint to get that
straightened out.  My apologies for any confusion caused by this
problem.

-- 
Mickey Rowe     (rowe@lepomis.psych.upenn.edu)