The megalodon (C. megalodon, Greek: mega(lo-) = large, odon = tooth, or large tooth) is an extinct species of shark that could reach enormous sizes. The megalodon appeared around 18 million years ago (in the Miocene) and became extinct around 1.5 million years ago. It dominated the temperate seas of the world with virtually no enemies; it could reach a length of 18 meters. It is closely related to the modern white shark. Megalodon could open its mouth up to 2 meters. Megaselachus megalodon is a synonym of Carcharodon megalodon or Carcharocles megalodon. To this day, fossil teeth of megalodon are regularly found; the rest of the cartilage skeleton has usually decayed. Its fairly large teeth are very characteristic (pyramidal).