Re: Dinosaur teeth

["Thomas R. Holtz, Jr." <th81@umail.umd.edu>]

At 11:44 PM 3/5/98 EST, you wrote:
>
>Does anyone know if a chemical or structural analysis of dinosaur teeth has
>ever been done to see if the actual enamel survives (vs fossilization).
>
>If enamel does fossilize completely it would be at a much slower time frame
>than dentin, cementum or bone.  Does anone knows the time frame.

You may wish to check out:

Bocherens, H. 1997.  Chemical composition of dinosaur fossils.  pp. 111-117.
IN Currie, P.J. & K. Padian (eds.), Encyclopedia of Dinosaurs.  Acadmeic Press.

In the short form: most dinosaur (and other) fossil bone, dentine, and
enamel *IS* the original hydroxlyapatite.  The idea that the minerals have
mostly been replaced is a myth: it DOES happen, but is a lot rarer than
older paleo books suggest.  Permineralization (the filling in of pore spaces
with minerals deposited out of ground water, but leaving the original
minerals intact) is much more common.

Rates of change will be highly variable, and are due as much (or more) to
local ground water conditions as anything else.

As you note, given the microstructure of enamel, there is reason to suspect
it is less susceptible to external influences.  This is part of a project
I'm actually helping with, with an isotope geochemist and an undergrad or
two.  (And people think all I do is cladograms... :-)

Thomas R. Holtz, Jr.
Vertebrate Paleontologist     Webpage: http://www.geol.umd.edu
Dept. of Geology              Email:th81@umail.umd.edu
University of Maryland        Phone:301-405-4084
College Park, MD  20742       Fax:  301-314-9661