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The Malacostraca (Greek: "soft shell") are the largest subgroup of crustaceans. They include decapods (such as crabs, lobsters and shrimp), stomatopods (mantis shrimp) and krill. There are 22,000 members in this group. It represents two thirds of all crustacean species. The first malacostracans appeared in the Cambrian period.[source?]

Malacostraca
Eoph MagelaT site2.jpg
Eophreatoicus, a fresh water isopod from Australia.
Scientific classification
Kingdom:
Phylum:
Subphylum:
Class:
Malacostraca

Latreille, 1802
Subclasses

Eumalacostraca
Hoplocarida
Phyllocarida
See text for orders.

The classification of crustaceans is currently being debated. Some think Malacostraca is a class and others think it is a subclass.

MorphologyEdit

 
General malacostracan layout

Malacostraca have heads with six segments. They have a pair of antennules and a pair of antennae. They also have mouthparts. There are appendages near the mouthparts, called maxillipeds. They have five pairs of walking legs. The first pair is formed like a pincer. There are eight thoracic segments. There are six abdominal segments. They are used for swimming. Members of Malacostraca have compound stalked or sessile eyes. They have a two-chambered stomach and a centralized nervous system.

ClassificationEdit

 
Lysiosquilla maculata, a mantis shrimp

Class Malacostraca Latreille, 1802