Sealife guideSharks: guardians of the oceanMarine vertebrates

Last updated on 08/22/2025 at 10:42 PM

Sharks, like rays, belong to the class of chondrichthyans, which includes all cartilaginous fish. Within this class, sharks are part of the subclass of elasmobranchs.

Classification

Sharks are classified into eight orders, mainly according to the shape and arrangement of their different fins:

the order Carcharhiniformes29 species

Explore the sharks of the order Carcharhiniformes, the largest shark group, characterized by their nictitating membranes, diverse sizes and varied diets ranging from small fish to marine mammals.

Bonnethead shark
(Sphyrna tiburo)

Grey reef shark
(Carcharhinus amblyrhynchos)

Oceanic whitetip shark
(Carcharhinus longimanus)

Small-spotted catshark
(Scyliorhinus canicula)

the order Hétérodontiformes4 species

Explore the sharks of the order Heterodontiformes, known for their distinctive blunt heads and unique teeth, which help them crush hard-shelled prey like sea urchins and mollusks.

Crested hornshark
(Heterodontus galeatus)

Horn shark
(Heterodontus francisci)

Port Jackson shark
(Heterodontus portusjacksoni)

Zebra bullhead shark
(Heterodontus zebra)

the order Hexanchiformes2 species

Discover the sharks of the order Hexanchiformes, easily recognized by their six or seven gill slits, ancient lineage and deep-sea habitats.

Broadnose sevengill shark
(Notorynchus cepedianus)

Frilled shark
(Chlamydoselachus anguineus)

the order Lamniformes6 species

Explore the sharks of the order Lamniformes, known for their large size, powerful swimming and iconic species like the great white and mako sharks.

Great white shark
(Carcharodon carcharias)

Longfin mako
(Isurus paucus)

Pelagic thresher shark
(Alopias pelagicus)

Short fin mako
(Isurus oxyrinchus)

the order Orectolobiformes11 species

Explore the sharks of the order Orectolobiformes, also called carpet sharks, including species like the whale shark and bamboo sharks, often found resting on the sea floor or camouflaged among reefs.

Nurse shark
(Ginglymostoma cirratum)

Raja epaulette shark
(Hemiscyllium freycineti)

Tawny nurse shark
(Nebrius ferrugineus)

Whale shark
(Rhincodon typus)

the order Pristiophoriformes0 species

Explore the sharks of the order Pristiophoriformes, also known as sawsharks, recognized by their long, toothed snouts used to detect and capture prey on the sea floor.

the order Squaliformes3 species

Explore the sharks of the order Squaliformes, commonly called dogfish sharks, which are small to medium-sized deep-sea sharks known for their spiny dorsal fins and slow, stealthy movements.

Greenland shark
(Somniosus microcephalus)

Leafscale gulper shark
(Centrophorus squamosus)

Spiny dogfish
(Squalus acanthias)

the order Squatiniformes2 species

Explore the sharks of the order Squatiniformes, known as angel sharks, which have flattened bodies and broad pectoral fins, allowing them to lie camouflaged on the sea floor while waiting to ambush prey.

Common angelshark
(Squatina squatina)

Pacific angelshark
(Squatina californica)

Description

Shark anatomy

Geographic range and habitat

Sharks are found in all the world's seas and oceans, across all latitudes and at all depths: from warm tropical waters to icy polar waters, from shallow waters along coasts and coral reefs to the deep sea !

Some shark species are pelagic, while others are benthic and live resting on the seafloor.

Diet

Most often resting during the day, sharks feed mainly at night, when they are most active in searching for prey.

Sharks are top predators at the apex of the marine ecosystem's food chain. Their diet is mainly carnivorous but highly varied: mollusks for nurse sharks, squid, octopuses, fish of all sizes, sea lions, seals and even plankton for the whale shark and the basking shark.

The whale shark feeds only on plankton ! © Krzysztof Odziomek | Dreamstime.com

To protect their eyes when attacking prey, some sharks like the great white shark can roll their eyes back, while others like the tiger shark have a very strong, semi-transparent nictitating membrane that covers their eyes like a third eyelid !

Reproduction

Typically in fish, fertilization is external after the release of male and female gametes into seawater. Sharks, however, are an exception to this rule and have internal fertilization. The male shark's pelvic fins have evolved into reproductive organs called claspers.

All sharks have internal fertilization, but the development and feeding of the embryo vary depending on the species. Some sharks are oviparous, others are ovoviviparous, the most common reproductive mode and a few are viviparous, such as the lemon shark.

The capsule containing the shark egg is called a mermaid's purse © Anke Van Wyk | Dreamstime.com

For oviparous sharks, the eggs are enclosed in small transparent sac-like capsules. These capsules are called « mermaid's purses ».

Did you know?

There are currently more than 380 species of sharks worldwide !
The largest fish is a shark: the whale shark, measuring up to 65 feet long !

Discover sharks

Blacknose shark
(Carcharhinus acronotus)

Blacktip shark
(Carcharhinus limbatus)

Brownbanded bamboo shark
(Chiloscyllium punctatum)

Copper shark
(Carcharhinus brachyurus)

Galapagos shark
(Carcharhinus galapagensis)

Great white shark
(Carcharodon carcharias)

Greenland shark
(Somniosus microcephalus)

Grey reef shark
(Carcharhinus amblyrhynchos)

Horn shark
(Heterodontus francisci)

Leafscale gulper shark
(Centrophorus squamosus)

Nurse shark
(Ginglymostoma cirratum)

Raja epaulette shark
(Hemiscyllium freycineti)

Sandbar shark
(Carcharhinus plumbeus)

Silky Shark
(Carcharhinus falciformis)

Spotted wobbegong
(Orectolobus maculatus)

Whale shark
(Rhincodon typus)

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Requin cuivre
(Carcharhinus brachyurus)