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Re: The question of beaks in simplistic terms



Nick Gardner (ratites637@hotmail.com) wrote:
;

<Did you actually mean to type, "many if not all ornithischians [...]
without premaxillary teeth are _assumed_ to have a beak on the
premaxilla"?>

  Ah. I forgot a clause, it seems. Here's what it should read as:

  "...[M]any if if not all ornithischians, aside from a prior mentioning
of *Edmontosaurus annectens* (though toothless) with premaxillary teeth
are _assumed_ to have a beak on the premaxilla."

<"Yandusaurus" multidens certainly seems to resemble Agilisaurus,
especially in the premaxillary teeth. Wasn't A. suggested at one point to
be a VERY basal Marginocephalian?  If so, is it possible that "Y"
multidens is also another VERY basal Marginocephalian?  Or are these type
of teeth basal to Cerapoda [= Neornithischia]?>

  *"Y." multidens* lacks most of the premaxilla, including any
tooth-bearing portion it may have had (I assume there to be teeth to begin
with, but this is based on its apparent basal ornithopodan position, all
forms of which had 5 teeth). My original skull and the basis of the image
linked previously compensated for assuming that, after Peng, the two
species were related closely (*A. multidens* and *A. louderbacki*). I
would not really know if *"Y." multidens* has been referred to the
Marginocephalia; Dong has referred the species to *Xiaosaurus* at one
point, but this is considered rather weak, based only on his assumption of
a single species in the Xiashaximiao Fm. at Dashanpu; the material of
*Xiaosaurus* does, however, have some featyures similar to some
pachycephalosaurids and psittacosaurids, and this has been interestying,
but *Xiasosaurus* and *"Y." multidens* are relatively distinct.

  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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