Since ancient times, people found fossilized bones and shells of strange creatures. For thousands of years they did not understand who these remnants belonged to, and tried to explain their findings somehow: these bones belonged to giants and monsters, or to antediluvian fauna. Gradually, scientists began to understand that such remains belonged to animals, and finally they declared: long before the appearance of people, these bizarre animals, fishes and lizards existed on Earth, and those fossils were their remains.