[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Re: Reptilians Get Cheeky

> <<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.

Hmm... my cheeks at least don't contract dorsoventrally. There are muscles
in the cheeks that pull the lips around, but I haven't found any that move
my jaws...

> 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.

Yes. Again, iguanas don't chew AFAIK.

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

Sounds very plausible. I never wrote about muscular cheeks...