Sharks

Scientific name : Selachimorpha

Sharks (supraorder Selachimorpha) are well-known creatures, due to their conspicuous features, which make them rather feared.
They are streamlined fish, with a cartilagineous skeleton and dermal denticles which protect their skin from harm and parasites, other than easing their swimming.
They can be found all over the world, and the shark species can be quite small or very big, such as the whale shark. They have no gas bladder, and their teeth (one of the most conspicuous features of the group) are laid in many rows, which number changes among the species. Their tail is also very peculiar, with an elongated upper part (heterocercal).