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Fossilized Shark Teeth on the Internet |
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There are about 13 different processes grouped in two phases (Taphonomic and Diagenetic) that effect the tooth during fossilization, many of them destructive. Very few shark teeth go through the 20 thousand to 100 thousand or so years it takes to fossilize a tooth without significant damage. One paleontologist estimates that perhaps only 10 to 15% actually make it. See the next photo below for an example of one that almost did not make it.
After the megalodon lost a tooth, it settled to the bottom of the ocean and was covered by sediment. For the first few years the dentin absorbed water and became swollen. This swelling process cracked the enamel coating and began to separate it from the underlying dentin. The blade enamel is almost never cracked out to the edges because there is no dentin under the enamel in these areas and the enamel itself is too hard to absorb water. In many teeth there is also a noticeable separation between the blade enamel and the bourrelet enamel on both sides. (Believe it or not there IS a bourrelet on the flat side of a megalodon tooth - it's just not as noticeable.)
During the next 20 - 100 thousand years, two things happened:
(A.) Much of the pulp and dentin were dissolved by the water and replaced by precipitant substances, one molecule at a time. The "spaces" in between this material was also filled in by this same compound. (The same thing happens with "petrified wood" where the original material is replaced by minerals and only the shape of the original wood remains.) The tooth enamel, being much harder, is not affected except that it takes up the color of whatever impurities are in the sedimentary material the tooth falls in. This makes for the vast variety of colors of the fossil teeth. The original enamel, dentin and pulp were white, just like modern shark teeth.
(B.) Over time, the tooth was buried deeper under tons of ocean floor and the material (matrix) around the tooth dried out and possibly heated up which caused the tooth to dry out. This caused the tooth to dehydrate and crack even more, generally in the root area (dehydration stress crack). You can see how this works as a physical process in dried-up "mud flats".
For the above reasons, most teeth are found to have cracks in the enamel (hydration swelling) and root (dehydration stress), and some have much of the enamel and root cracked away. The enamel forms an attachment to the surrounding matrix that is stronger than it's weakened (cementum) attachment to the underlying (fossilized) dentin and comes away with the matrix when the tooth and matrix are separated. This is what causes "enamel peel"
The bourrelet enamel is particularly susceptible to being shattered or lost because it is thinner than the blade enamel and is over the area of maximum dentin swelling.
We are not going to show photos for every type of this kind of damage - just look at any megalodon tooth photo on the Internet.
We will show, however, one tooth in our collection that exhibits most of the things that can go wrong during fossilization:
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