An order of primitive copepod crustaceans first discovered in 1911 in shallow waters off the coast of Norway and now known in the North Pacific as well as the North Atlantic. Copepods, along with insects and nematode worms, are one of the three mega-abundant groups of multicelled animals on Earth. Members of the Platycopioida (platycopioids) are tiny copepods. None has a body length greater than 1.0 mm (0.04 in.) and little is known of the biology of the 11 described species. Their scientific significance stems from their position as the first offshoot at the base of the copepod evolutionary tree. They retain a suite of exceptionally primitive characters that generate insight into the features presumed present in the ancestors of all copepods. These primitive characters relate to the segmentation pattern of the antennules and to the arrangement of spines on the five pairs of swimming legs.