due to several unique conserved morphological characteristics (autapomorphy) such as its naked filamentous gills and thin thoracopods and by molecular studies.

There have been many theories of the location of the order Euphausiacea. Since the first description of Thysanopode tricuspide by Henri Milne-Edwards in 1830, the similarity of their biramous thoracopods had led zoologists to group euphausiids and Mysidacea in the order Schizopoda,