A phylum of microscopic marine worms related to Rotifera and Micrognathozoa, mainly characterized by complex cuticular structures in the pharynx and a monociliated skin epithelium. Discovered in the 1920s on the German coast but not described until 1956, Gnathostomulida have since been reported from many sheltered sandy shores around the world. With fewer than 100 known species, this is one of the smallest animal phyla.