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The Malacostraca are the largest subgroup of crustaceans, and include most of the animals that non-experts recognise as crustaceans, including the decapods (such as crabs, mole crabs, lobsters and true shrimps), the stomatopods or mantis shrimps, and krill. They also include the huge group of amphipods, and the only substantial group of land-based crustaceans, the isopods (woodlice or sowbugs and related species).
The classification of crustaceans is currently being debated, and the Malacostraca are regarded by some authors as a class and by others as a subclass.
Their characteristics include:
- Five pairs of walking legs
- The first pair of legs are often modified to form pincers
- Cephalothorax covered by a carapace
- Abdomen behind, often used for swimming
- Appendages near the mouth; these are called maxillipeds
- Two-chambered stomach
- Centralised nervous system
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