One of the pleasures of beachcombing on Georgia sea islands is spotting rare treasures such as castoff shark's teeth. All sharks have several sets of sharp triangular teeth that are constantly shed and replaced. Some of these teeth eventually find their way to the beach. Shark's teeth are white when shed, however the teeth found on the beach among the drifts of small clam shells are mostly colored tan, gray, or black. The color results from the teeth being buried in oxygen depleted sediment for a long enough time, usually ten thousand years or more, for the calcium phosphate in the enamel to be slowly exchanged for iron and other minerals. This process preserves the teeth, which otherwise would dissolve in sea water. So the teeth found on the beach are fossils from long-dead sharks that swam the seas centuries before humans vacationed on the Georgia shore.
The less than inch long shark teeth arrayed around the penny in the photo above were found by our family on Nannygoat Beach on Sapelo Island. They belong to common species found off the coast that grow up to 6 to 14 feet in length: sand tiger sharks, sandbar sharks, finetooth sharks (the thin black tooth in the photo), lemon sharks, and hammerhead sharks. The two and a half-inch long tooth in the photo is a fossil, from an extinct species of mackerel shark that lived about 55 million years ago; this tooth is the size of teeth of the great white shark.
However, the teeth of the largest known ancient shark, megalodon, which lived from 16 to 2.6 million years ago and which reached nearly 60 feet in length, were 5 to 6 inches in size. The photo below shows a 5 1/2 inch fossil megalodon tooth (centimeter-scale ruler), next to teeth of a modern great white shark that seem puny in comparison.
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