Crabs shrimps and lobsters are the most familiar malacostracans. With 30000 species this is the largest class of Crustaceans. The malacostracan trunk is typically composed of 14 segments plus the telson. The first 8 form the thorax, the last 6 the abdomen. All bear appendages.
Four malacostracan orders are illustrated here: the Amphipoda, the Isopoda, the Stomatopoda and the Decapoda (crabs and lobsters). Many of these animals are of great importance as food, pests and parasites. They also include the few crustacea which have successfully colonised land.