Diversity of Fishes

BIO 365

Fusiform body type

typical fish shape; cigar-shaped; circular or elliptical in cross section

Lateral Compression body shape

made for slow speeds, highly maneuverable

vertical depression body shape

flattened; slow-moving bottom dwellers

elongated body shape

long-body, round in cross section (snake-like)

superclass agnatha

jawless fishes, 2 orders, Myxiniformes and petromyzontiformes

Order Myxiniformes

Hagfishes - no eyes, teeth only on tounge, 6 tentacles around mouth, no paired fins, 2 nostrils

Order Petromyzontiformes

lampreys - well-developed eyes, teeth in oral disc, no tentacles around mouth, one nostril, no paired fins

Superclass Gnathostomata

Contains all jawed-fishes

Class chondrichthyes

cartilaginous fishes - contains orders squaliformes, rajiformes, and chimaeriformes

Order Squaliformes

dogfish sharks (126 species); fusiform body, have placoid scales, heterocercal tail, gill slits behind head

Order Rajiformes

Skates (300 species); flattened body, pectoral fin expanded for swimming, mouth and gill slits on ventral surface, holes behind eyes permit flow of water current

Order Chimaeriformes

ratfish (30 species); tapering tail, skin essentially naked, poisionous dorsal spine

Superclass Euteleostomi

Bony vertebrates

Class Sarcopterygii

Fleshy-finned fishes, contains order lepidosireniformes

Order Lepidosireniformes

Lungfishes (5 species); elongated body, large cycloid scales, fins are long and filamentous

Class Actinopterygii

Ray-finned fishes (most species rich class of vertebrates)

Subclass Chondrostei

Primitive bony fishes - Order Acipenseriformes

Order Acipenseriformes

sturgeons and paddlefish (27 species); sturgeon - snout elongate, mouth and barbels undersurface of snout, have scutes, heterocercal tail. paddlefish - elongated body, paddle-shaped snout, heterocercal tail, few patches of ganoid scales

Subclass Neopterygii

Modern Bony fishes

Order Lepisosteiformes

gars (7 species); cylindrical body with heavy ganoid scales, jaws are elongated and well-toothed, short dorsal fin set far back, abbreviate heterocercal tail

Order Amiiformes

bowfin (1 living species); elongate dorsal fin, bony gular plate in throat region, depressed mouth, thin cycloid-like scales

Order Anguilliformes

eels (730 species); snake-like body, scales are absent or rudimentary, no pelvic fins, sometimes lacking pectoral fins

Order Clupeiformes

herrings and anchovies (350+ species); body expremely compressed, many have keeled abdominal scutes, scales cycloid, soft fin-rays only

Order Salmoniformes

salmon and trout (150 species); body is slender or fusiform, commonly have adipose fin, all fin-rays soft, scales are cycloid

Order Cypriniformes

minnow, suckers, and shiners (3000+ species); cycloid scales, soft fin-rays, no adipose fin

Order Siluriformes

catfishes (2800 species); body either naked or covered in bony plates, elongate barbels frequently present, spines in dorsal and pectoral fins, adipose fin usually present

Order Gadiformes

cods and hakes (550 species); body typically fusiform, 2 or 3 dorsal fins, 2 anal fins

Order Scorpaeniformes

scorpionfishes (1400 species); body often depressed, head with large mouth and often spines, dorsal/anal/pelvic fins with spines

Order Perciformes

perch-like fishes (10,000+ species); structurally very diverse but most with fin spines, thoracic pelvic fins, and ctenoid scales

Order Pleuronectiformes

flatfishes and flounders (650 species); juveniles are bilaterally symmetrical but become flattened during maturation, eyes migrate to one side of head

Order Tetraodontiformes

triggerfishes, trunkfishes, and puffers (350 species); body often stout or angular, fused teeth, mouth forms a beak

Cycloid Scales

Ctenoid Scales

Ganoid Scales

Placoid Scales