Branchiura is a group of parasitic crustaceans of uncertain position within the Maxillopoda. They are thought to be primitive forms but there is no fossil recorded. The subclass contains one family with around 130 species, all of which are ectoparasites on fish. A few exceptions have been found on amphibians. Classes Branchiopoda Cephalocarida Malacostraca Maxillopoda Ostracoda Remipedia The crustaceans (Crustacea) are a large group of arthropods (55,000 species), usually treated as a subphylum. ... Sub-classes Thecostraca Tantulocarida Branchiura Pentastomida Mystacocarida Copepoda Maxillopoda is a class of crustaceans, characterised by a reduction of the abdomen and its appendages. ... In object-oriented programming, subclass is a class that is derived from another class or classes. ... Scientific classification or biological classification refers to how biologists group and categorize extinct and living species of organisms. ... In biology, a species is a kind of organism. ... A parasite is an organism that lives in or on the living tissue of a host organism at the expense of that host. ... Atlantic herring, Clupea harengus, the most abundant fish species in the world. ... Orders Subclass Labyrinthodontia - extinct Subclass Lepospondyli - extinct Subclass Lissamphibia   Anura   Caudata   Gymnophiona Amphibians (class Amphibia) are a group of animals that include all tetrapods (four-legged vertebrates) that do not have amniotic eggs. ...