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Reptilians Get Cheeky



David Marjanovic (David.Marjanovic@gmx.at) wrote:

<<a protoceratopsian without cheeks looks very awkward, because
these animals chewed and would have needed to prevent the food
from falling out. I can't buy it. I wouldn't expect exact
identity to mammalian cheeks (and lips) anyway, because we're 
talking of convergences...>>

  Mammal cheeks, just so thet it's known to one and all, are
formed by particular pinnate muscles called buccals, which are
really rather thick and actually assist in the closing of the
jaw and contract during the chewing cycle to mash food. You can
check this my taking an apple (for instance) and feeling your
cheeks as you chew. Only mammals have this type of muscle.
Reptiles that acheive herbivory may even have indented tooth
rows, such as iguanas, but these are not surmounted by any form
of integument.

and Waylon Rowley (whte_rbt_obj@yahoo.com) wrote:

<There are a variety of herbivorous lizards that don't have
cheeks and manage just fine. I do agreee that the protoceratops
drawing looks a bit odd. It's almost as if the skin and muscles
on the jaw were cut off....gives the head a skeletonized look.
Nasty. I don't like it. But who cares if I like it? If there's
reason to believe this is how they looked, we shouldn't let our
biases get in the way of good science.>

  Waylon is very right. Liking that the cheeks "look better"
doesn't provide an excuse to use them.

<Maybe they had stiff lips that slid past eachother to help keep
food in, or tongues that kept food from falling out. I don't
think these guys were very good at masticating their food
because they probably wouldn't need gastroliths if they were
(i've never heard of cow gastroliths, have you?). Besides, I
thought ceratopsians *sliced* their food. I'm no ceratopsian
expert, so I yield to the superior intellects of others on the
list with regards to this subject. So, maybe they just plucked a
leaf off, sliced it a few times and gulped it down. If feeding
was that fast, you wouldn't need cheeks.>

  The very narrow oral cavities of ornithischians suggests that,
for all the processing of food an animal the size of
*Triceratops* or with the gut of a pachycephalosaur had, the
oral cavity is depressingly small for the style of feeding they
have been suggested as having unless the jaws bore some
collateral means of containing unprocessed food. Doesn't mean
they need accesory jaw muscles for processing. A simple skin
barrier is all that's neccesary. Greg Paul's illustrations
apparently demonstrate this, as one can observed from the
closed-jaw illustrations showing the line of the tooth row -- he
may have a different reason for doing this, but this way my
impression. "Cheeks" of an animal that processes mean do not
need to be muscular unless they're doing someing else besides
holding their food _in_. I draw my cheeks as if they were simple
skin imbedded with scales. My ornithischians are veiwable now on
my site at

  http://www.geocities.com/Qilongia/pics.html

  and follow the link to Ornithopods or Ceratosaurs, or the "in
progress" Ceratopsians, which has my skull (from the side!) of
*Goyocephale*. Tons more ornithischians to render that fit here,
need to figure out how to render *Hypsilophodon*....


=====
Jaime A. Headden

  Aaaaaaaaaaaaaaaaaaaahhhhhhhhhhhhhhhhhhr-gen-ti-na
  Where the Wind Comes Sweeping Down the Pampas!!!!

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