Before they were recognized as shark’s teeth, Megalodon teeth were mistakenly identified as rocks that had fallen from the moon, or as the petrified tongues of dragons and giant serpents. In 1666, while studying the teeth of great white sharks, naturalist Nicolaus Steno made the realization that these “tongue stones” were actually shark’s teeth.
His biggest discovery was that these teeth had kept their form, but not their composition – that they’d been turned into rock over a very long period of time. In other words, they had become fossils.
Since then, scientists have found hundreds of fossilized Megalodon teeth and spinal segments known as centra. Because a shark’s skeleton is made up of cartilage, which dissolves quickly in ocean water, these are the only Megalodon remains that have survived over millions of years.
Scientists are able to learn a lot about Megalodon from these fragments. For example, experts can determine a Megalodon’s age at death by examining the centra. Each centra contains growth rings, sort of like a tree. By counting the rings, their color, and how far apart they are, scientists are even able to determine a Megalodon’s growth rate.