Megalodon (full name Otodus megalodon) means "Big Tooth" - a suitable moniker for what may be the biggest shark to have ever lived. This absolute unit grew to be an  average of 15 meters in length. Its  razor-sharp teeth were as large as a human's hand, reaching an average diagonal length of 18 centimeters. Because sharks' skeletons are mostly made out of cartilage, the only  fossils paleontologists have of  Megalodon are teeth, vertebrae, and coprolites. This makes it difficult to reconstruct what it would have looked like in life, but we can assume that it looked like a huge basking shark or thick great white.   Megalodon prowled the oceans of the Neogene Period in subtropical  and temperate waters. As juveniles,  they stayed in shallow coastal environments, but as adults they preferred deeper water offshore. Their prey of choice were smaller cetaceans, and several whale bones  have been discovered with massive cuts from Megalodon teeth. They  competed with predatory whales like  Livyatan for prey, which is one  factor that lead to their extinct- ion. Although popular Shark Week documentaries claim that this giant  species might still exist, it is  impossible that it has survived.  It was not equipped to dine on the  larger whales that evolved, it could  not compete with killer whales, and  could not take the colder climate.