When did the megaladon vanish and what can it tell us about our oceans?

An artist's impression of carcharocles megalodon, the largest shark that ever lived.

The fearsome carcharocles megalodon or monster shark grew up to 18 metres in length. It was perhaps the largest fish and most dangerous predator the world has seen. The shark was found all around the planet and then became extinct.

The giant shark left an abundant fossil record from the middle Miocene (15.9 to 11.6 million years ago) to the Pliocene (5.3 to 2.6 million years ago) and its triangular fossilised teeth were once thought to be the tongues of dragons.

Until now, scientists have been unable to pinpoint exactly when the monster disappeared from the oceans, but recent research by biologists Catalina Pimiento from the University of Florida and Christopher Clements from the University of Zurich, have put the date at around 2.6 million years ago, at the end of the Pliocene and beginning of the Pleistocene era. It was during the Pleistocene (2.6 million to 11,700 years ago) that baleen whales – including the blue whale – reached their gigantic size. The results have been published in PLOS one.

It is understood that the disappearance of top feeders, or apex predators, can trigger profound changes throughout the marine food chain. In the present day, the number of sharks in the world's oceans is declining, so the fate of the megalodon is therefore of "significant interest", the researchers say.

The researchers used an Optimal Linear Estimation (OLE) model to arrive at the estimated time of extinction, plus their knowledge of evolutionary trends in whales.

"Despite the limitations and uncertainties of the fossil record, the study of the time of extinction of C. megalodon provides a baseline to understand the establishment of the modern structure and function of gigantic filter-feeding whales," the authors say.

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