Fish classification

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)


 Subclass Crossopterygii (Latimeria)

 Subclass Actinopterygii (Bony fishes).

Romer’s classification (1959)


Class PLACODERMI (Pterichthyes; Coccostei; Acanthodi)


Subclass Elasmobranchi  (Sharks, dogfishes, skates, rays)

Subclass Holocephali (Chimaera)


Subclass Sarcopterygii

Order CROSSOPTERYGII (Latimeria)

Order DIPNOI (Lungfishes)

Subclass Actinopterygii (All bony fishes)

Parker & Haswell’s classification (1967)


Class PLACODERMI (6 Subclasses)


Subclass Selachi (Sharks and Rays)

Subclass Bradyodonti (=Holocephali) (Chimaera)


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.


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)