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Re: D-sectioned teeth



David Marjanovic wrote-

> >  0- Stokesosaurus (Madsen, 1974)
>
> I assume that's illustrated?

The preserved tooth is said to be subcylindrical.

> In PDW there are repeated mentionings of slightly-or-so D-shaped pmx teeth
> in *Allosaurus*. I should have made that clearer. I assume it has a
> comparable state to troodontids.

Ken Kinman wrote-

> Aren't at least two of Utahraptor's premaxillary teeth asymmetric
> enough to be considered D-shaped?  And perhaps Dromaeosaurus sort of
> part-way between that shape and troodonts more symmetric shape?
> Just how far back must the carinae shift in order to qualify as forming
> a D-shape?

It's not asymmetry that makes tyrannosauroid premaxillary teeth D-shaped.
Ceratosaurus and most avetheropods/neotetanurines (like Allosaurus) have
asymmetrical premaxillary teeth (Holtz, 2000).  Tyrannosauroid premaxillary
teeth are actually roughly symmetrical, as are troodontids'.  While you
might be able to imagine a D-shape in the cross section of dromaeosaurid
premaxillary teeth, just saying "D-sectioned" isn't what people mean when
they refer to how distinctive tyrannosauroid premaxillary teeth are.
They're a rounded rectangular shape, with the labiolingual dimension much
larger.  The carinae are positioned in the lingual corners of the rectangle,
making them sharp corners unlike the labial ones.  This is what the
character "D-shaped premaxillary teeth" is really getting at, which is not
found in dromaeosaurids, troodontids or allosaurids.

Mickey Mortimer