An order of the crustacean superorder Syncarida, the most primitive of the Eumalacostraca. The families Anaspididae and Koonungidae have living representatives, while the Clarkecarididae are true fossils. The families Gampsonychidae and Palaeocarididae, formerly included in this order, now are assigned to a new order, Palaeocaridacea. The Anaspidacea arose during the Paleozoic Era, and the recent species are now restricted as living fossils to fresh-water habitats in Tasmania and South Australia (not New Zealand). They exhibit a great adaptability to special habitats. The first thoracic somite is incorporated with cephalic tagmata.