Re: Rugops

["Jaime A. Headden" <qilongia@yahoo.com>]

Some data has been used to support *Carnotaurus* as a scavenger, including
the so-called "delicate" teeth, good for nipping "weak" meat that's slowly
rotting anyway. The jaws were apparently "weak" because of the "loose"
connection between dentary and post-dentary elements, etc. These same
features are seen in *Rugops,* but to a more limited extent. The main
difference seems to be that the teeth form a more "hack-saw" variant than
a series of vertical knives as in *Allosaurus* or *Carnotaurus.* When I
look at the jaws of scavengers like vultures and jackals and coatimundi, I
see long narrow snouts with low profiles, good adaptations for getting
into narrow areas and crevices. But in *Rugops*, we have a broad, high
skull, rounded, ovate and not the slightest bit tapered or triangular,
with the teeth set back from the most rostral point of the skull (the
anterior portion of the premaxillary nasal bar). As in *Carnotaurus,* the
point of greatest strength for the jaw appears to be in a vertical
direction situated at the ascending process of the maxilla, linked to
Rayfield's "hatchet-head" model for *Allosaurus* and Mazetta's comparable
model for *Carnotaurus.*

Mazetta, G.V.; Fariña, R.A.; and Vizcaíno, S.F. 2000. On the palaeobiology
  of the South American horned theropod *Carnotaurus satrei* Bonaparte.
  _GAIA_ 15: 185-192.

Rayfield, E.J.; Norman, D.B.; Horner, C.C.; Horner, J.R.; Smith, P.M.;
  Thomason, J.J.; and Upchurch, P. 2001. Cranial design and function in a
  large theropod dinosaur. _Nature_  409: 1033-1037.

  In comparison, scavengers often require some form to manipulate or
bypass the obstacles of bones or, as in hyenas, _through_ them, to which
comparison of the bites of bone-crunchers are neccessary. This has been
substantiated to some degree by Erickson, Hurum, and Currie, as in:

Erickson, G.M.; Van Kirk, S.D.; Su J.; Levenston, M.E.; Caler, W.E.; and
  Carter, D.R.  1996. Bite-force estimation for *Tyrannosaurus rex* from
  tooth-marked bones. _Nature_ 382: 706-708.

Hurum, J.H. and Currie, P.J. 2000. The crushing bite of tyrannosaurids.
  _Journal of Vertebrate Paleontology_ 20(3): 619-921.

Hurum, J.H. and Sabath, K. 2003. Giant theropod dinosaurs from Asia and
  North America: Skulls of *Tarbosaurus bataar* and *Tyrannosaurus rex*
  compared. _Acta Palaeontologica Polonica_ 48 (2): 161-190.

  This may be exemplitive, in that the jaw design between abelisaurids and
tyrannosaurids are remarkably similar with fused interdental plates,
thickened jaw and roofing bones, and interlocking mechanisms with regards
to most of the cranial bones. A scavenger, plucker, messy-eater will
likely not need to process this degree of food. It is my hypothesis that,
despite the massive difference between their teeth, the shortening of the
teeth and the form of the tooth bearing bones would lead one to suspect
that some abelisaurids were likely bone-crunchers, not pluck and pick
eaters, as in coatis and jackals. One can presume that some theropods from
Africa, such as *Suchomimus,* were much better adapted for scavenging with
long narrow snouts and long teeth for gripping deep viscera. If an animal
would need to shove it's 2 foot head into some convenient orifice instead
of MAKING one, that kind of defeats the purpose?

  I would propose *Rugops* as being a game hunter, a real _shikari_ if you
will, rather than a scavenger. Like *Tyrannosaurus* or
*Carcharodontosaurus,* the foramina atop the nasal may have supported the
keratin of the snout, much more elaborate and blood-filled than in
*Carnotaurus,* perhaps, rather than a full-snout sheath. The teeth appear
to be pretty large and functional, so I cannot see why or how a "beak"
would begin to have a functional effect given that it will not occlude
with another beak OR the lower jaws. However, the highly keratinized skin
of the face is likely given the highly rugose facial bones, this should be
true for half of the skull in some tyrannosaurids, or perhaps
*Monolophosaurus,* which has similar rugosities but larger teeth.

  Cheers,

=====
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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