Eucarida is a superorder of the Malacostraca, a class of the crustacean subphylum, comprising the decapods, krill, and Angustidontida.

[3] Eucarida is a diverse and abundant group, comprising the following three orders: The members of the Euphausiacea are commonly called krill and are all marine shrimp-like species whose pleopods (abdominal appendages) function as swimmerets.

[4] Decapoda is a group with 15,000 species[5] which have 5 pairs of thoracopods and a well-developed carapace that covers the gills (which are exposed in krill).

The decapods are further subdivided on the basis of the gill structure into two suborders Dendrobranchiata (prawns) and Pleocyemata, which is further subdivided into several infraorders, such as the Caridea (true shrimp), the Stenopodidea (boxer shrimp) and the Anomura and the Brachyura (crabs) and so forth.

[6][7] Lastly, there is an extinct order that contains only one family, Angustidontidae, which in turn contains two genera, Angustidontus and Schramidontus.