Fish can be broadly divided into bony and cartilaginous species. Unlike the thousands of species of bony fish in the sea, sharks 'skeletons are made up entirely of cartilage, and the 350-odd species of sharks account for almost all the cartilaginous fishes.
魚類被大分為硬、軟骨兩種，和大海裡成千上萬種硬骨魚兒不同的是，鯊魚骨骼全是軟骨，三百五十多種的鯊魚也幾乎就是軟骨魚類的全部。