All sharks and rays belong to the class of cartilaginous fishes. Their skeleton is built of hardened cartilage, as opposed to bone. The body muscles are joined to the spine by connective tissues. All cartilaginous fishes are carnivores. They have electro-sensitive pores on their head to track down their prey.
Cartilaginous fishes reproduce partly oviparous, partly viviparous.
Unlike bony fishes, fertilization of the eggs happens inside the females. Many species of cartilaginous fishes, in particular sharks, are endangered. Every year, tens of millions die in floating nets and in the commercial hunt for shark fins. The shark fin soup industry is perhaps the sharks biggest enemy, and unless consumers become educated, many species of shark may soon be extinct. Its caudal fin is almost as long as its body.