Vertebrate Diversity
Class Actinopterygii — Ray-finned Fishes

(Click on any image for larger version)

Order Polypteriformes — Bichirs

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

Order Acipenseriformes — Sturgeons & Paddle Fish

• Cartilagenous skeleton (secondarily derived)
• Heterocercal tail
• 2 families that appear very different:
  Sturgeons: 5 rows of bony scutes; protrusible downward-facing jaws (for bottom feeding), row of barbels
  Paddle fish: greatly elongated rostrum (used to detect electrical signals of prey)
• 28 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
• ≈33,000 species divided into ≈60 Orders

See also
Bony Fish Anatomy page

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
• >900 mostly marine species

(Order Osteoglossiformes)

• Arawans, Elephantfishes and relatives
• Elongated body
• Teeth on "tongue bones"
• Fewer than 16 rays in dorsal fin
• 244 species; fresh water, mostly in Africa

(Order Clupeiformes)

• Shad, herring, sardines
• Generalized bodies
• Usually have silvery bodies
• Lack lateral lines
• ≈400 species; pelagic; feed on plankton
• Many are commercially valuable

Order Cypriniformes

• Minnows, carp, loaches
• Lack adipose fin
• No scales on head
• Diverse body forms
• >4200 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
• ≈2300 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 usually small: nocturnal or in murky water
• >3700 species; worldwide mostly in fresh water

(Order Gymnotiformes)

• Neotropical Knifefishes
• Slender, elongated body with tapered tail
• Elongated anal fin along most of length of body (gymnotiform swimming)
• Weakly or strongly electrical
• 208 species; in fresh water

Order Salmoniformes

• Salmon & trout
• Mostly fairly large size
• Scales usually very fine
• 223 species; in northern hemisphere rivers (some anadramous)
• Some species commercially valuable

Percomorph Fishes

• The following Orders are part of a monophyletic clade of derived teleost fishes, the Percomorpha
• Previously, a number of these orders were placed in a large polyphyletic Order Perciformes (sensu lato), with over 10,000 species
• Recent extensive molecular studies have started to reveal the relationships among these groups
• Consequently, a number of new orders have been erected recently, but because many of the groups are united based on molecular data, it can be difficult to identify distinguishing characteristics
• The classification of this site follows: Nelson, J.S., et al. 2017. Fishes of the World, 5th ed. Wiley.

(Order Gobiiformes)

• Gobies
• Small fishes typically <10cm
• In most, pelvic fins fused to form disc-shaped sucker
• Often colorful
• Lack swim bladder, so are primarily benthic
• Most in shallow marine and brackish habitats; a few are fresh water
• >2150 species

(Ovalentaria insertae sedis)

• A group of families whose relationships are still uncertain
• Mostly small to medium sized
• Often colorful
• Marine waters, especially tropical reefs
• ≈750 species

Cichliformes

• Cichlids
• Mostly medium sized, oval, and laterally compressed
• Often colorful
• Complex pharnygeal jaws has allowed for a great deal of diversification
• Between 1700 and 3000 species, especially in East African lakes
• Fresh water in Neotropics and Africa

(Order Atheriniformes)

• Silversides & Rainbow fishes
• Elongated, streamlined fishes
• Silvery to colorful
• Reduced lateral line
• Rivers and brackish coastal waters
• ≈350 species

(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
• ≈280 species, pelagic in both marine and fresh water

Order Cyprinodontiformes

• Top-minnows, live-bearers, killifishes
• 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)
• 1257 mostly fresh-water species
• Many occur in harsh environments (brackish marshes, hot springs, isolated pools) unsuitable for other fish

(Order Carangiformes)

• Jacks, etc.
• Streamlined shapes
• Carangiform swimming, with sickle-shaped caudal fin
• Generally silver in color
• Fast-swimming pelagic marine fish
• 160 species

(Order Anabantiformes)

• Gouramis, bettas & snakeheads
• Labyrinth organ in head allows them to breathe air
• Typically somewhat deep-bodied
• Fresh water, especially slow-flowing, low O₂ waters in tropics
• ≈200 species

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
• ≈770 species of predominantly benthic marine fishes

Order Syngnathiformes

• Pipefishes, seahorses, seamoths
• Atypically shaped, usually elongated
• Body armored with various plates
• Small mouth at end of long snout
• Shallow marine waters
• ≈340 species

(Order Scombriformes)

• Tunas, mackerels, etc.
• Medium to large fishes
• Streamlined shape
• Often with series of small finlets behind dorsal fin
• Crescent-shaped caudal fin
• Color generally silvery
• Some (tunas) are endothermic
• Fast swimming pelagic ocean fishes
• ≈200 species

(Order Labriformes)

• Wrasses
• Protractile mouths; often with thick lips
• Complex pharyngeal jaws contribute to their diversity
• Mostly small and somewhat elongate bodies
• Dorsal fin usually along most of length of back
• Most are very colorful
• ≈630 species in shallow marine waters, especially coral reefs

Order Perciformes (sensu stricto)

• Perches and relatives
• Diverse, generalized fish with few distinctive characters
• Well developed spines in dorsal, pelvic & anal fins
• Some very colorful
• Occur in both fresh and marine waters
• >2200 species

Order Scorpaeniformes

• Rockfish, scorpionfish, sculpins, etc.
• Most are large-headed with large pectoral fin
• Spine on the operculum
• Often have enomous spines or armor plates
• >2000 mostly benthic and mostly marine species

(Order Spariformes)

• Breams & Porgies
• Small to medium size
• Mostly united by molecular data
• ≈300 marine & brackish waters

(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
• 325 benthic marine species, mostly in deep water
• See also Deep Sea Fish, below, for other examples

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
• 433 species; mostly tropical marine

• This section covers some deep-sea fishes of various orders (you will not need to know these orders) to highlight some of the distinctive adaptations of fishes living in the deep sea
• These will be mostly represented by models in lab due to a lack of specimens
• Among the adaptations to look for include:
  Enormous mouths & long teeth
  Weak bodies and reduced muscles
  Bioluminescent organs
  Large eyes
  Transparent skull with upward facing eyes

Models of Deep Sea Fish (scale approximate)