Malacostraca

Malacostraca; Temporal range:
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Arthropoda
Superclass:	Multicrustacea
Class:	Malacostraca; Latreille, 1802
Subclasses
	Eumalacostraca; Hoplocarida; Phyllocarida; See text for orders.

Malacostraca (from Neo-Latin; from Ancient Greek μαλακός (malakós) 'soft', and όστρακον (óstrakon) 'shell') is the second largest of the six classes of pancrustaceans just behind hexapods, containing about 40,000 living species, divided among 16 orders. Its members, the malacostracans, display a great diversity of body forms and include crabs, lobsters, crayfish, shrimp, krill, prawns, woodlice, amphipods, mantis shrimp, tongue-eating lice and many other less familiar animals. They are abundant in all marine environments and have colonised freshwater and terrestrial habitats. They are segmented animals, united by a common body plan comprising 20 body segments (rarely 21), and divided into a head, thorax, and abdomen.