Considered one of the greatest marine predators of all time, the Megalodon has inspired a number of works of fiction since it was first described in the 19th century. But while the scientific community classifies it as an extinct species today, some disagree, and believe that this sea monster could still be roaming our oceans today.

Otudus Megalodon is thought to have lived in all the world's oceans from the Aquitanian to the Zankee period, between 23 and 3.6 million years ago. It takes its name from the ancient Greek words Mégas (great/powerful) and Odoús (tooth), which literally translates as "Great Tooth". A fitting name, since this super-predator had teeth that sometimes exceeded 20cm in length, and were wider than a human hand. 

These teeth undoubtedly played a part in medieval folklore in Europe, since until the Renaissance, large fossilised triangular teeth (often found embedded in rock) were considered to be petrified tongues or the fossilised teeth of dragons or giant snakes.

It wasn't until 1667 that the Danish naturalist Nicolas Sténon recognised them as shark teeth, dispelling the myth about their origin. And finally, in 1843, the Swiss naturalist Louis Agassiz gave this extinct giant shark its first scientific name: Carcharodon Megalodon.

The extinction of the Magalodon questioned

The extinction of the Magalodon has been called into question by some, however, who put its disappearance at a much more recent date (between 10,000 and 5,000 years ago) based on testimonies from the 19th and 20th centuries.

One of these testimonies concerns two giant non-fossilised shark teeth brought up from the seabed by the HMS Challenger at the end of the 19th century. At the time, their age was estimated at around 10,000 years. 

However, a more recent (but approximate) dating would put them at between 11,000 and 24,000 years old, and there is no proof that they belonged to a megalodon, since the dentition of great white sharks and megalodons is physically very similar, so they could have belonged to great white sharks tending towards gigantism.

Another account can be found in Pierre Clostermann's "Des Poissons si Grands" (Such Large Fish), published in 1969. In it, the author describes an incident that had occurred 15 years earlier.

The captain of the cutter Rachel Cohen, remembering that his ship had been the victim of a violent collision during a storm off Timor, had stopped off in Adelaide to have her hull refitted. He was stunned to discover 17 very large shark teeth, embedded in the wooden keel and arranged in a semi-circle with a radius of almost a metre. The specimen was estimated at the time to be up to 24 metres long.

The average size of a megalodon is around 12 metres long, but the largest specimens can sometimes reach 20 metres, so such an estimate would be greatly exaggerated. But all the same, for the jaw span to reach such an impressive size, the shark in question must have been extraordinarily large.

Assuming that the testimony is not exaggerated, or that it is simply real, we can justifiably wonder whether the cutter did not cross the path of a living megalodon.

But once again, these are only eyewitness accounts. It is therefore impossible to state with any certainty that the incident actually took place.

In fact, it is difficult to describe the exact physique of the megalodon with any certainty, since it was a shark that, like modern sharks, had a skeleton composed mainly of cartilage, which deteriorates more quickly than bone and very rarely fossils.

So for a long time, researchers thought that the megalodon was a direct ancestor of the great white shark, because of the similar shape of their teeth. But in reality it was a cousin, descended from a common ancestor. The similarity of their teeth would therefore be due to a convergent evolution of the two species and not to a direct family link. 

These new assertions could disprove theories that the megalodon is alive and well, which are based on the discovery of very large teeth that are very recent in age. Since these teeth are physically closer to those of today's great white shark than they are to megalodon tooth fossils.

Furthermore, speculation that the megalodon became extinct very recently, or is still alive today, is still classified as cryptozoology, a pseudoscience that encompasses the study of animals whose existence has not been irrefutably proven.

Officially, and taking into account only recognised megalodon tooth fossils, the sea monster is thought to have become extinct 3.6 million years ago, and its disappearance is linked to a global cooling cycle with which it was unable to evolve.