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Re: The question of beaks in simplistic terms



David Marjanovic (david.marjanovic@gmx.at) wrote in response to Kris
Kripchak (MariusRomanus@aol.com):

  Kris:

<<1) Havin' teeth has not been shown to negate a beak.>>

  David:

<Sure.>

  I might want to add that many if not all ornithischians, aside from a
prior mentioning of *Edmontosaurus annectens* with premaxillary teeth are
_assumed_ to have a beak on the premaxilla; the premaxilla in these forms,
all the little non-iguanodonts, non-eurypodans, non-ceratopsomorphans,
etc. (i.e., "hypsilophodontians") have a relatively non-foraminated
premaxilla with teeth, and highly rugose texturing on parts. As a
parallel, the predentary, though pitted on the venter, usually has a
distinct lateral ridge that, above which, does not bear foramina but was
almost certainly covered in keratin. Some forms may not have a beak, some
may, we do not know. That premaxillary teeth show distinct lingual wear
rather than caudal carinate wear indicates that in some forms a
lower-beak/tooth wear was occurring; whether the predentary was covered in
keratin or not has never been questioned, to my knowledge, but should at
least be subjected to some question or investigation.

  Finally, to illustrate this point, I have always drawn
"hyspilophodontians" with premaxillary beaks, with work stretching back
some few years, including:

  http://qilong.8m.com/Yandusaurus_multidens_head.jpg (dating to the end
of 1997, after I joined the DML)

  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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