Mike . . .
You may want to look in Bernhard Peyer, COMPARATIVE ODONTOLOGY, University
of Chicago Press (1968).
The caption for Plate 44b says this:
Vertical section through a pavement tooth of a pycnodont from the Lower
Cretaceous of Texas; polarized. In the center the dark orthodentine, whose
dentinal tubules are visible; above it, lighter, the cap of modified dentine;
left and right along the margin the stronly birefringent true enamel also
encloses the base of the modified dentine. 22:1.
Perhaps what you see as a column-like structure is the substructure of
orthodentine from which the "cap" of modified dentine has separated.
-----------Harry Pristis
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In a message dated 7/10/2006 12:42:06 P.M. Eastern Standard Time,
mike@oceansofkansas.com writes:
All,
I'm currently working with pycnodont fish specimens from the
Smoky Hill
Chalk (Late Cretaceous) ... and am somewhat confused regarding
the
terminology used to describe the teeth. *Most fish teeth are acrodont
(attached directly to the bony surface of the jaws and other tooth
bearing cranial elements):
*
*http://www.oceansofkansas.com/FossilFish/Enchodus/e-petro7.jpg*
*
Pycnodonts
were small to medium-sized, deep-bodied bony fish with
rounded and
flattened teeth that are well adapted for crushing food
items (similar to
modern parrot fish). In the case of pycnodonts,
however, I note that
the enameloid crowns appear to be sitting on
distinct, column-like
structures that penetrate deep into the bone ...
This may just be a
specialized area of bone under the crown, but it
certainly looks like and
appears to function like a
root...
http://www.oceansofkansas.com/FossilFish/Pycnodont/CHALKPYC.jpg
http://www.oceansofkansas.com/FossilFish/Pycnodont/1991-84.jpg
Typically,
the tooth crowns are collected without the "roots" being
attached:
http://www.oceansofkansas.com/FossilFish/Pycnodont/03BLUE28.jpg
...but
I have recovered others with a portion of the structure still in
place.
Can anyone clarify this issue for me? ... please reply off
list.
Regards,
* Mike Everhart
Adjunct Curator of
Paleontology
Sternberg Museum of Natural History
Fort Hays State
University, Hays,
KS
www.oceansofkansas.com
http://www.oceansofkansas.com/Pycnodont.html