Fish classification


(Dr. Girish Chandra)

Fishes have been classified in different ways from time to time. Earliest classification was proposed by J. Muller (1844) who proposed 7 subclasses in class Pisces.

Muller’s classification (1844)


            Subclasses:  DIPNOI (Lung fishes); TELEOSTEI  (Bony fishes);  GANOIDEI  (Polypterus, Amia, Lepidosteus); ELASMOBRANCHI  (Cartilagenous fishes); MARSIPOBRANCHI  (Cyclostomes); LEPTOCARDII  (Amphioxus).

Berg’s classification (1940)


            Class PLACODERMI  (Pterichthyes; Coccostei; Acanthodi)

            Class ELASMOBRANCHI  (Cartilagenous fishes)

            Class HOLOCEPHALI  (Chimaera)

            Class DIPNOI  (Lung fishes)

            Class TELEOSTOMI

 Subclass Crossopterygii (Latimeria)

 Subclass Actinopterygii (Bony fishes).

Romer’s classification (1959)


            Class PLACODERMI  (Pterichthyes; Coccostei; Acanthodi)

            Class CHONDRICHTHYES

                        Subclass Elasmobranchi  (Sharks, dogfishes, skates, rays)

                        Subclass Holocephali  (Chimaera)

            Class OSTEICHTHYES

                        Subclass Sarcopterygii

                                    Order CROSSOPTERYGII  (Latimeria)

                                    Order DIPNOI  (Lungfishes)

                        Subclass Actinopterygii  (All bony fishes)

Parker & Haswell’s classification (1967)


            Class PLACODERMI (6 Subclasses)

            Class CHONDRICHTHYS

                        Subclass Selachi (Sharks and Rays)

                        Subclass Bradyodonti (=Holocephali) (Chimaera)

            Class OSTEICHTHYS

                        Subclass Crossopterygii  (Latimeria)

                        Subclass Actinopterygii  (Rayfin bony fishes)

            Class DIPNOI (= CHOANICHTHYES) (Lung fishes)


COMBINED CLASSIFICATION (After Romer, 1959 and Parker & Haswell, 1967)


            Class PLACODERMI (6 Subclasses) Extinct.

            Class CHONDRICHTHYS

                        Subclass Elasmobranchi

Marine with placoid scales; pelvic fins modified as claspers; tail heterocercal; mouth ventral; cloaca present; spiracle present; operculum present.

                                    Superorder CLADOSELACHI (Extinct Sharks)

Paired fins biserial with a median axis; vertebra not differentiated; tail fin variable.

                                    Superorder SELACHI  (Modern cartilaginous fishes)

Paired fins finfold type; tail fin heterocercal; males with claspers; 5 pairs of gill slits; operculum absent; No air bladder; placoid scales present.

                                                Order Pleurotremata (Shaks and Dogfishes), 400 species.

Body cylindrical; gill slits laterally placed; pectoral fins small; eyes laterally placed.

                                                Order Hypotremata (Skates and Rays), 450 species.

Body dorsoventrally flattened; gill slits ventrally placed; pectoral fins large and fused on the lateral margins; bottom dwellers.

                        Subclass Holocephali (Chimaera), 30 species.

Four pairs of gills; notochord persists; teeth modified as crushing plates; mouth with lips; holostylic jaw suspension; tail whip-like; operculum present; spiracles absent but a single nostril present; skin naked with scattered placoid scales.

            Class OSTEICHTHYS

                        Subclass Crossopterygii  (Latimeria), 2 species.

Internal nares present; fins lobed except the first dorsal fin; scales with cosmine layer; air bladder lung-like; jaw suspension autostylic; notochord persists and vertebrae unossified;

                        Subclass Actinopterygii  (Rayfin bony fishes), 22,000 species.

Fins with fin rays; tail fin homocercal; scales cycloid and ctenoid; internal nares absent; air bladder present but no lungs; jaw suspension methystylic.

                                    Superorder CHONDROSTEI (35 species)

Skeleton partly cartilaginous; ganoid scales present; two internal nostrils present; air bladder two-lobed and ventral.

                                                Order Polypteriformes (Polypterus), 10 species.

                                                Order Acipenseriformes (Acipenser; Polyodon), 25 species

                                    Superorder HOLOSTEI (8 species)

Skeleton partly cartilaginous; teeth sharp; ganoid scales on body; air bladder lung-like; tail fin homocercal; vertebrae opisthocoelous.

                                                Order Amiiformes (Amia calva)

                                                Order Semiontiformes (Lepidosteus), 7 species.

                                    Superorder TELEOSTEI (20,000 species)

                                                Skeleton bony; tail homocercal; scales cycloid and ctenoid.

                                                Order Clupeiformes (Herrings; Salmons, Sardines)

                                                Order Scopeliformes (Bombay duck)

                                                Order Cypriniformes (=Ostariophysi) (Labeo, Catla,                                                              Mystus, Clarias, Wallago, Heteropneustes)

                                                Order Anguilliformes (Eels)

                                                Order Beloniformes (Flying fishes)

                                                Order Syngnathiformes (Sea horse and Pipe fish)

                                                Order Mastacembeliformes (Eel-like Mastacembelus)

                                                Order Ophiocephaliformes (Ophiocephalus)

                                                Order Symbranchiformes (Eel-like Amphipnous)

                                                Order Perciformes (Lates; Perca)

                                                Order Scorpaeniformes (Scorpion fish)

                                                Order Pleuronectiformes (Flat fishes)

                                                Order Echeneiformes (Sucker fish)

                                                Order Tetraodontiformes (Tetrodon; Diodon; Ostracion)

                                                Order Lophiiformes (Angler fishes)