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Re: Dinosaur toot numbers

Maybe Jon is waiting in the wings before coming in on this one, and it is
a pity Ralph Chapman is not regular here anymore....

George Olshevsky (Dinogeorge@aol.com) wrote:

<It may be neither, as Anatotitan longiceps has a longer dentary than
either Edmontosaurus annectens or Anatotitan copei. With these animals a
longer dentary means more tooth rows or, more appropriately, columns. Have
to check Lull & Wright; it might have detailed tooth-row-column

  I would not count on the total jaw length in *Anatotitan copei* as a
reference to tooth count, as unlike other hadrosaurs, the mandible of *A.
copei* is protracted relative to the others at both the post-coronoid
ramus and the edentulous portion of the dentary, with elongation of the
predentary coupled with the reduction of a ventral curvature, making the
jaw longer relatively, but the tooth-bearing portion remains the same
size. Chapman and Brett-Surman (1990, in the _Dinosaur Systematics_
volume) have done some work on the morphometrics of the skulls of
*Edmontosaurus regalis* vs. *Anatotitan copei* that showed most
differences involved between the two are elongations of the snout and some
widening of the temporal region, probably to affect the changes in the jaw
musculature positions, that differ from all other *Edmontosaurus* (incl.
"Anatosaurus"). This results in the tooth-bearing portion of the jaw to
about one-fourth the length of the skull, rather than about one-third.

  To my knowledge, *Anatosaurus longiceps* was synonymized with *A. copei*
in 1990, when has this changed? 'Sides, all taxa exhibit some variation in
jaw length....

  Mike Corriss asks how ceratopsids might differ, but these forms have
only two/three ranks in each file of the jaw, and the number goes about a
hundred or so in the whole skull. I may be wrong.


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.

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