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'''Sharks''' are approximately 350 species of cartilaginous fish of the order Selachimorpha, inhabiting the world's oceans and several freshwater lakes and rivers.
'''Sharks''' are approximately 350 species of cartilaginous fish of the order Selachimorpha, inhabiting the world's oceans and several freshwater lakes and rivers.
==Description==
Sharks vary in appearance, shape, and size, so there is no absolute description of a typical shark. In general, all sharks with several exceptions share the following characteristics:
*A skeletal system made entirely of cartilage, with the vertebrate extending to and forming the claudal (tail) fin's upper lobe.
*A ventrally-located mouth with the upper jaws unattached to the skull, enabling the animal to extend both jaws forward to take in prey.
*Skin covered with denticals, a type of placoid scale rough to the feel and related to teeth.
*Teeth arranged in a "conveyor belt"-fashion, enabling continual replacement over the lifetime of the animal.
===Orders and Families===
====[[Squaliformes]]====
Dogfish; order representing 7 families and 113 species of shark, with the spiny dogfish possibly the most abundant fish of any kind in the world's oceans.
*Bramble sharks (Echinorhinidae)
*Dogfish (Squalidae)
*Roughsharks (Oxynotidae)
====[[Hexanchiformes]]====
*Frilled sharks (Chlamydoselachidae)
*Cow sharks (Hexanchidae)
====[[Pristiophoriformes]]====
*Sawsharks (Pristiophoridae)
====[[Squatiniformes]]====
*Angelsharks (Squatinidae)
====[[Heterodontiformes]]====
*Bullhead sharks (Heterodontidae)
====[[Orectolobiformes]]====
*Collared carpetsharks (Parascyllidae)
*Blind sharks (Brachaeluridae)
*Wobbegongs (Orectolobidae)
*Bamboosharks (Hemiscyllidae)
*Zebra sharks (Stegostomatidae)
*Nurse sharks (Ginglymostomatidae)
*Whale shark (Rhiniodontidae)
====[[Lamniformes]]====
*Sandtigers (Odontaspididae)
*Goblin shark (Mitsukurinidae)
*Crocodile shark (Pseudocarchariidae)
*Megamouth shark (Megachasmidae)
*Thresher sharks (Alopiidae)
*Basking shark (Cetorhinidae)
*Mackerel sharks (Lamnidae)
====[[Carcharhiniformes]]====
*Catsharks (Scyliorhinidae)
*Finback catsharks (Proscylliidae)
*False catsharks (Pseudotriakidae)
*Barbelled houndshark (Leptochariidae)
*Houndsharks (Triakidae)
*Weasel sharks (Hemigaleidae)
*Requiem sharks (Carcharhinidae)
*Hammerhead sharks (Sphyrnidae)
== Behavior ==
== Behavior ==