Sharks have roamed our seas for at least 400 million years, long before dinosaurs or even trees appeared. Yet, if you wander along fossil-rich beaches, like Florida’s famous Peace River, you’ll mostly find teeth, not whole bodies. That’s because shark skeletons are made of cartilage, which doesn’t fossilize well. Their teeth, however, are made of hard enameloid and resist decay, making them the most common shark fossils.
How Do Shark Teeth Become Fossils?
Sharks continually shed teeth, some species lose thousands over a single lifetime. When a tooth falls, it often settles into sediment and is buried. Over millennia, minerals like silica and calcite seep in through groundwater, filling tiny pores in the tooth, a process called permineralization, turning it into a fossil. The availability of different minerals explains why fossil teeth can be grey, black, orange, or even blue.
Why Teeth, and Little Else, Survive
Because sharks are cartilaginous, their skeletons disintegrate quickly. Cartilage lacks the minerals needed to survive burial and fossilize. That leaves teeth, and sometimes vertebrae or dermal denticles, as the only parts likely to become fossils. In rare, low-energy environments with rapid burial, even some cartilage can be preserved, but that’s the exception.
What Fossil Teeth Tell Us
Fossil teeth can be ecological time machines. Their shapes and serrations reveal diets, needle‑like teeth for small fish, flat ones for crushing shellfish, and serrated serratia for large prey like marine mammals. By analyzing chemical composition, such as strontium or fluorine, scientists can determine the habitat and migration patterns of ancient sharks.
For example, the Florida Museum’s vast collection of over 115,000 shark teeth helps date geological formations, reconstruct Pleistocene ecosystems, and track ancient biodiversity shifts. Megalodon teeth, some reaching a staggering 17 cm, reveal that these apex predators once grew longer than a school bus.
Connect the Past with the Present
Every fossil tooth you find is literally a piece of deep time: evidence of shark species that have come and gone, shifting environments, and geological transformations. These teeth inspire us to protect today’s sharks, with innovations like Shark Stop wetsuits, so that future generations won’t just study in museum sandboxes but experience healthy, thriving oceans firsthand.
Let fossil shark teeth remind us: sharks are among Earth’s most enduring species. Let’s protect them, before they’re gone.