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Crustaceans

Crustacea
Temporal range: 511–0 Ma
Cambrian to Recent
A segmented animal is seen from the side. It has a long antennae and small black eyes; one pair of legs is much more robust than the others; the body is slightly arched and each segment carries a pair of appendages. The whole animal is translucent or a pale brown colour.
Abludomelita obtusata, an amphipod
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Clade: Pancrustacea
Subphylum: Crustacea
Brünnich, 1772
Classes and subclasses

Thylacocephala? †
Branchiopoda

Phyllopoda
Sarsostraca

Remipedia
Cephalocarida
Maxillopoda

Thecostraca
Tantulocarida
Branchiura
Pentastomida
Mystacocarida
Copepoda

Ostracoda

Myodocopa
Podocopa

Malacostraca

Phyllocarida
Hoplocarida
Eumalacostraca

Thylacocephala? †
Branchiopoda

Remipedia
Cephalocarida
Maxillopoda

Ostracoda

Malacostraca

Crustaceans (Crustacea /krʌˈstʃə/) form a large, diverse arthropod taxon which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill, woodlice and barnacles. The crustacean group is usually treated as a subphylum, and thanks to recent molecular studies it is now well accepted that the crustacean group is paraphyletic, and comprises all animals in the Pancrustacea clade other than hexapods. In other words, some crustaceans are more closely related to insects and other hexapods than they are to certain other crustaceans.

The 67,000 described species range in size from Stygotantulus stocki at 0.1 mm (0.004 in), to the Japanese spider crab with a leg span of up to 3.8 m (12.5 ft) and a mass of 20 kg (44 lb). Like other arthropods, crustaceans have an exoskeleton, which they moult to grow. They are distinguished from other groups of arthropods, such as insects, myriapods and chelicerates, by the possession of biramous (two-parted) limbs, and by their larval forms, such as the nauplius stage of branchiopods and copepods.


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