Vertebrate Diversity
Class Osteichthyes — Bony Fishes

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Characteristics

• Large size (~2m)
• Distinctive caudal fin with 3 divisions
• Fins muscular, limb-like ("lobed")
• Skeleton mostly cartilagenous
• Modern species are marine, in deep water
• 2 extant species (first one discovered in 1938)

Characteristics

• Elongated bodies
• Dorsal, caudal, anal fins fused into single rear fin
• Fins flipper-like or reduced to long filaments
• Paired lungs
• Live in tropical rivers or swamps prone to drying
• 6 living species

Characteristics

• Extinct lobe-finned fish related to tetrapods
• Late Devonian, 385 mya
• Up to 4 m long
• Shares with tetrapods various skull characteristics, internal nostrils and labyrinthodont teeth (with folded enamel)
• Fins have distinct humerus, ulna, radius and femur, tibia, fibula
• Lived in fresh water

Characteristics

• Very diverse: 42 Orders, 431 Families, over 27,000 species
• Fins supported entirely by fin rays
• Single dorsal fin (though it may be subdivided)
• Ganoid (primitive) or cycloid (derived) scales
• 4 primitive Orders (<50 species total); rest belong to clade "Teleostei"

See also
Bony Fish Anatomy page

Order Polypteriformes — Bichirs

• Covered in thick, interlocking ganoid scales
• Elongated body
• Dorsal fin with multiple finlets, each supported by spine
• Paired lungs
• 10 species; Africa

Order Acipenseriformes — Sturgeons & Paddle Fish

• Cartilagenous skeleton (secondarily derived)
• Heterocercal tail
• 2 families that appear very different:
  Sturgeons: note 5 rows of bony scutes; protrusible downward-facing jaws (for bottom feeding)
  Paddle fish: note greatly elongated rostrum (used to detect electrical signals of prey)
• 27 species; Temperate rivers; some sturgeons are anadramous

Order Lepisosteiformes — Gars

• Elongated, tubular body; 1-4 m long
• Greatly elongated, well-toothed jaws
• Large, non-overlapping ganoid scales
• Ambush predators
• 7 species; North and Central America

Order Amiiformes — Bowfin

• Mobile maxilla (shared with Teleosts)
• Cycloid scales (shared with Teleosts)
• Single large lung
• Stout body
• Skull and jaws largely solid
• 1 species; southeastern North America

Characteristics

• Includes vast majority of bony fishes
• Mobile maxilla and premaxilla
• Homocercal tail
• Wide variety of body forms
• Divided into 38 Orders

See also
Bony Fish Anatomy page

Order Osteoglossiformes

• Arawans, Elephantfishes and relatives
• Elongated body
• Teeth on "tongue bones"
• Fewer than 16 rays in dorsal fin
• The most primitive of the teleost fishes
• Fresh water, mostly in Africa

Order Anguilliformes

• True Eels
• Greatly elongated snake-like body
• Lack pelvic fins and often lack pectoral fins
• Dorsal & anal fins contiguous with caudal fin: tail pointed
• Scales deeply imbedded or absent
• 730 mostly marine species

Order Clupeiformes

• Shad, herring, sardines
• Generalized bodies
• Usually have silvery bodies
• Lack lateral lines
• 215 species; pelagic; feed on plankton
• Many are commercially valuable

Order Cypriniformes

• Minnows, carp, loaches
• Lack adipose fin
• No scales on head
• Diverse body forms
• 2700 species; fresh waters, mostly in Northern Hemisphere
• Taxonomic note: This and the following 2 orders (Characiformes and Siluriformes) constitute most of a monophyletic clade (the Ostariophysi) of mostly fresh water fish

Order Characiformes

• Characins, Tetras, Piranha
• Laterally compressed, fusiform bodies
• Adipose fin present
• Diurnal: generally silvery or colorful and with large eyes
• 1550 species; fresh waters of Latin America, Africa

Order Siluriformes

• Catfishes
• Skin scaleless or with bony plates
• Flattened head, broad mouth
• Mouth surrounded by 1-4 pairs of barbels ("whiskers")
• Eyes small: nocturnal or in murky water
• 2600 species; worldwide mostly in fresh water

Order Salmoniformes

• Salmon, trout, and relatives
• Mostly fairly large size
• Scales usually very fine
• In rivers or anadramous
• Some species commercially valuable

(Order Lophiiformes)

• Frogfish, batfish, anglerfish
• In most, dorsal spine modified into lure
• In some, pectoral fins modified for walking
• Odd appearance, often cryptically shaped & colored

(Order Beloniformes)

• Dorsal and anal fin similar in size and close to tail
• Several distinctive families, including:
  Needlefishes have very long jaws
  Flying fishes have greatly enlarged pectoral fins for gliding above the water

Order Cyprinodontiformes

• Top-minnows, live-bearers, pupfish
• Small size (< 15 cm)
• Pelvic fins usually absent
• Rounded caudal fin
• Some have internal fertilization and are viviparous
• Males of some have a gonopodium (modified anal fin for mating)
• Many occur in harsh environments (brackish marshes, hot springs, isolated pools) unsuitable for other fish

Order Syngnathiformes

• Pipefishes, seahorses, seamoths
• Atypically shaped, usually elongated
• Body armored with various plates
• Small mouth, usually at end of long snout
• Shallow marine waters

Order Scorpaeniformes

• Rockfish, lionfish, etc.
• Large-headed
• Large, rounded pectoral and dorsal fins
• Have either numerous spines or armor plates
• 1300 bottom-dwelling marine species

Order Perciformes

• Diverse with varied shapes
• Typically are moderately elongate and deep-bodied
• Typically have double or 2-part dorsal fin
• Lack adipose fin
• Pelvic fins positioned close to pectoral fins (or absent)
• Typically have relatively large eyes and mouth
• Ctenoid scales
• Most species-rich order of vertebrates (>9000 species)
• Includes majority of fishes associated with coral reefs
• Taxonomic Note: relationships uncertain; likely to be paraphyletic or polyphyletic

Order Pleuronectiformes

• Flatfishes, flounders
• Body greatly flattened laterally
• Lay on one side on ocean bottom
• One eye moves to opposite side of face
• Dorsal, anal, & caudal fins almost completely surround body

Order Tetraodontiformes

• Puffers, triggerfish, etc.
• Non-streamlined, bulky shape
• Slow (ostraciform) swimmers
• Hard, powerful jaw with beak-like teeth
• Most specialize on hard or spiny prey
• 340 species; mostly tropical marine