The megalodon (pronounced /ˡmɛ.gə.ləˌdɒn/ or MEG-a-la-don; meaning "big tooth" or in Greek as μέγας 'οδόντος) was a giant shark that lived in prehistoric times, between about 18 million to 1.5 million years agoa[›] and was the apex predator of its time. It is the largest carnivorous fish known to have existed, and quite possibly the largest shark to have ever lived. It is believed that the average size of the megalodon was between 12 metres (39 ft) and 18 metres (59 ft). This species is a member of the lamnidae family but its classification is in dispute and a new genus has been proposed. Fossil evidence has revealed that megalodon fed upon large animals, including the early whales.
Some cryptozoologists argue that this shark might still be alive today, probably living in deep waters, and often cite the examples of coelacanth and megamouth shark to support their claims. However, such beliefs have earned no credibility in the mainstream scientific community.
The Swiss naturalist, Louis Agassiz, gave this shark its scientific name, Carcharodon megalodon in 1835, in his research work Recherches sur les poissons fossiles (Research on fish fossils), which he completed in 1843. Due to the dental similarities of the teeth of the great white shark, Carcharodon carcharias, and megalodon, Agassiz proposed Carcharodon as the genus. In-short, this shark is termed C. megalodon by shark researchers. However, it is often dubbed the "mega-tooth shark" or "giant white shark."