Since shark skeletons
are
composed of cartilage instead of bone, often the only parts of the shark to
survive as fossils are teeth. Fossil shark teeth date back hundreds of millions
of years. The most common, however, are from the Cenozoic Era (65 million
years ago to present).
How a Tooth Becomes
A
Fossil
A tooth become a fossil
when it is buried in sediment (or other material) soon after being lost from a
shark's mouth. The sediment precludes oxygen and harmful bacteria from reaching
the tooth and destroying it. The general fossilization process varies greatly
depending on the exact situation. In general it takes approximately 10,000
years for a tooth to become a true fossil.
Why Fossil Teeth
Are Different
Colors
The color of a tooth is
determined solely by the color of sediment in which it is buried while
fossilizing. The tooth absorbs minerals from the surrounding sediment. As the
minerals replace the natural structure of the tooth, the tooth becomes the same
general color as the sediment. Therefore, color is not an effective indicator
of the age of a tooth. The most common color for shark teeth is a black root
with a grayish crown. Different colors are more uncommon and significantly
increase the value of a tooth.
