On our earth, there is a very old creature called shark. They appeared about 500 million years ago, 300 million years earlier than the birth of dinosaurs. It can be said that they are “big men of bone ash” in biology.
We are very familiar with the name of “shark”, but we are very strange. We say that we are familiar with the name because we all know this kind of creature, and we say that we are unfamiliar because we know very little about them.
There are at least 440 shark species that can be distinguished by the current level of knowledge in the world. There are more than 500 shark species recorded in the “sharks of the world” series. Some of them are larger in size and we call them large sharks.