A copepod order of crustaceans containing four species. Mormonilla minor and M. phasma were described by Wilhelm Giesbrecht in the late 1800s; M. polaris and M. atlantica were described by Georg Ossian Sars and Richard Norris Wolfenden, respectively, in the early 1900s. The status of a fifth species in a second genus, Thomas Scott's Corynuropis tenuicaudatus, remains uncertain. In 1992, males of the order were collected and described for the first time.