In the first century AD Pliny the Elder recorded that Romans thought the huge triangular stones they found were serpent tongues that fell from the sky during lunar eclipses, and Renaissance nobles dipped these tongue stones in wine to detect poison. In 1616 Fabio Colonna burned one and found carbon, proving it organic, and in the 1660s Nicolas Steno compared them with the teeth of a great white’s head and concluded they were ancient shark teeth, a leap that helped found stratigraphy. Otodus megalodon ruled the oceans from about 23 million to 3.58 million years ago. It was long filed with the great white in Carcharodon but now sits in the extinct Otodontidae; its similar teeth are convergent evolution, and it took about 12 million years for the lineage to lose its side cusplets. With a cartilage skeleton, its size comes mostly from teeth: roughly 47 to 80 feet at maximum and 50 to perhaps over 100 metric tons.

Finite element analysis puts its bite at 108,000 to 182,000 newtons, about ten times a modern great white. It rammed whale rib cages, kept its muscles warm with a rete mirabile, and nitrogen and zinc isotopes in its teeth place it higher on the food chain than great whites. Its pups, 6 to 13 feet at birth, grew up in warm, shallow nurseries such as the Gatun Formation in Panama, the Calvert Formation in Maryland, and Bone Valley in Florida. When Pliocene cooling locked water in ice, those nurseries vanished, baleen whales moved to cold polar seas the shark could not tolerate, and smaller, efficient early great whites outcompeted young megalodons. The episode also dismantles the Mariana Trench survival myth.

• A megalodon jaw could open more than 100 degrees and held over 250 teeth in five rows.
• Its teeth were reinforced against the twisting force of head shaking bites.
• Healed compression fractures on fossil whale bones show high speed ramming attacks.
• Growth rings in rare calcified vertebrae suggest a lifespan of 88 to 100 years.
• Its disappearance lifted pressure on baleen whales and may explain the blue whale’s giant size.