A phylum of free-living marine invertebrates less than 1 mm long. They are segmented and lack internal ciliation (see illustration). Kinorhyncha, formerly called Echinoderida, are sometimes included in the rejected superphylum Aschelminthes, since their fluid-filled body cavity is probably a pseudocoel, or false coelom. Kinorhynchs are benthonic, generally dwelling in mud or sand from intertidal to deep-sea habitats. Two orders are generally recognized, Cyclorhagida and Homalorhagida.