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Re: Baryonychine Crests and Processes

White Rabbit Object (anyone remember Jurassic Park :) ) aka
"Waylon Rowley" (whte_rbt_obj@yahoo.com) wrote:

<It seems to me that a large spinosaur with a 5-6 foot long
skull and a similarly-sized neck would have a little difficulty
pulling *large* fish and possibly sharks/young crocodilians from
the waters it fed in. Sooooooooo....where do the massive muscles
required to lift such weight attach on the spinosaur skull,
neck, and back? Obviously, there is the nuchal crest at the back
of the skull above the supraoccipital, but I'm wondering if the
so-called "cruciate processes" which branch laterally from the
median nasal crest, and the knob associated with them, is
basically an accessory nuchal crest which provided additional
surface for the ligamentum nuchae to insert. In my hypothetical
spinosaur, the median nasal crest is a snout-stiffening ridge,
the cruciate processes (and the rugose knob above and between
them) and the nuchal crest all support a massive cervical
musculature that runs up to the dorsal sail, where they anchor
securely. So, I end up with a hump-backed (hump-necked,
actually) spinosaur. Behind this mass of muscle would be a fat
storage, I assume.>

  The cruciate crest is just that, cross-shaped. It has a caudal
ridge-like component, and is mounted on the median of the skull
in front of the eyes. The surface of the bone between that and
the supraoccipital crest is the frontal bones and the parietal
bridge, onto which, in no extant archosaur, no are muscles
mounted. So, presumably, the data suggesting nasal mounting of
craniocervical musculature is not well-substantiated.

  The supraoccipital is actually quite tall in baryonychine
spinosaurids, but not as high in *Irritator* itself. The nuchal
ridges are well-defined and the skull was quite tall with
sufficient leverage to offer exceptional load-bearing on the
cervico-occipital transition. Also, the neck of *Suchomimus*
appears to have a natural non-sigmoid arch, a condition seen in
*Monolophosaurus* as well (pers. obs. and presumptive candidate
for my SVP poster, but I decided to leave it off for the sake of
seeing the material in person, or a cast thereof :) ), which
would increase leverage in the neck and, presumably, and give
the head sufficient bearing to lift a 300-lb. lungfish (dipnoan).

Jaime A. Headden

  Where the Wind Comes Sweeping Down the Pampas!!!!

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