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an order (or subclass) of crustaceans. The wormlike body is up to 1 mm long. The head has a separate anterior part, the acron. The antennae, the palps of the mandibles and maxillae, and the maxillipeds serve for crawling. The four free thoracic somites have short, unsegmented limbs. There are six abdominal somites, five of which have no limbs. The last abdominal somite ends in claw-like appendages. Mystacocarida are dioecious. The larva—the metanauplius—emerges from an egg and molts nine times, gradually transforming into an adult. There is one genus, Derocheilocaris, with four species. The crustaceans inhabit the minuscule spaces between small grains of sand (up to 0.2 mm in diameter) on marine beaches, usually a little higher than the tidal line. One species, D. galvarini, is found at a depth of 25 m. Mystacocarida feed on small organic particles and are able to survive considerable variations in salinity and temperature. They are found near the coasts of Southern Europe, southern Africa, and North and South America.