Formation and Uses of Shark Tooth Fossils

How Fossilized Shark Teeth Form and are Used in Culture and Science

Jul 1, 2009

A shark tooth fossil is more than just a relic of evolution. Traditionally used as tools and as decoration, how are these fossils formed and what else are they used for?

A shark skeleton is composed of cartilage. Unlike mammalian bone, cartilage does not easily survive the fossilization process. As a result, there are very few shark skeletons in the fossil record. There is, however, an abundance of shark teeth.

Shark teeth are composed of dentine and enamel, more durable substances than cartilage. When a shark dies, it is heavier than the surrounding water. Lacking a flotation bladder, the dead shark sinks. Over time, the flesh and supporting cartilage are dissolved, and only the teeth remain.

A living shark, over the course of its lifetime, can shed and replace many thousands of teeth. Sharks have multiple rows of teeth. Those at the back are angled towards the inside of the mouth, and over time, move forward into an upright position, pushing out existing teeth or replacing lost ones in a process known as polyphyodont dentition. The shed teeth fall to the seabed. Gradually, these teeth are covered by mineral-rich sediment.

How Shark Teeth Become Fossils

This sediment covering prevents bacteria and oxygen from reaching and damaging the tooth. In a process called permineralization, the tooth absorbs minerals in the sediment. The minerals replace the tooth enamel and dentine. Over thousands of years, it is this chemical exchange that preserves the tooth and creates what is known as a fossil.

Shark Fossils as Primitive Tools

Many cultures found that shark tooth fossils made excellent tools, as shark teeth fossils retain their sharpness and the mineralization process makes the shark teeth incredibly tough. For example, the Polynesians used shark teeth fossils to make weapons and for fashioning domestic tools for cooking, cleaning and carving.

Shark Tooth Jewelry

In Hawaiian culture, wearing a shark tooth was thought to harness the shark's power as a predator, and fossilized shark teeth were often worn as necklaces by the Kanaka Koa, or warrior caste. Wearing such a pendant is also said to offer divers protection from shark attack, and shark tooth fossil necklaces and bracelets are an unusual and popular gift.

Shark Teeth Fossils as Evolutionary Indicators

According to the Florida Museum of Natural History Ichthyology Department, sharks have evolved into the approximately 400 known modern species over 400 million years. The recovery of fossilized shark teeth allows ichthyologists to chart the evolution of different species of shark by comparing teeth found in different locations from different periods of history.

Of particular use are transitional teeth. These are the fossilized remains of sharks that are developing into another species. By tracking changes in the tooth form and structure, scientists can determine which ancient species were the precursors of modern sharks.

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The copyright of the article Formation and Uses of Shark Tooth Fossils in Paleontology is owned by Nicolas McGregor. Permission to republish Formation and Uses of Shark Tooth Fossils in print or online must be granted by the author in writing.