BIO 370 — Vertebrate Zoology
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Vertebrate Diversity
Class Actinopterygii — Ray-finned Fishes

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Osteichthyes Characteristics

  • Endochondral (from cartilage) bone
  • Operculum covers gill openings
  • Complex skull structure
  • Fin rays (lepidotrichia)
  • Air sac functions as lung or swim bladder
  • Ganoid, cycloid, or ctenoid scales
  • Most have homocercal tail

Actinopterygii Characteristics

  • Very diverse: 64 Orders, 453 Families, over 33,000 species
  • Fins supported entirely by multiple fin rays
  • Single dorsal fin (though it may be subdivided)
  • Ganoid (primitive) or cycloid (derived) scales
  • 4 primitive Orders (48 species total); rest belong to clade "Teleostei"
See also
Bony Fish Anatomy page

Primitive (Non-teleost) Ray-finned Fishes

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
Senegal Bichir, Polypterus senegalus, adult
Senegal Bichir, Polypterus senegalus, juvenile

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)
  • 28 species; Temperate rivers; some sturgeons are anadramous
River Sturgeon
River Sturgeon, Acipenser sp.
American Paddlefish, Polyodon spathula

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
Longnosed Gar
Spotted Gar, Lepisosteus oculatus
Longnosed Gar
Long-nosed Gar, Lepisosteus osseus
Alligator Gar
Alligator Gar, Atractosteus spatula

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
Bowfin Specimen
Bowfin, Amia calva
(see Bony Fish Anatomy page for a Bowfin skull)
Bowfin Specimen
Bowfin, Amia calva, closeup of head

Subclass Teleostei — Teleost Fishes


  • 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
Green Moray
Green Moray Eel, Gymnothorax funebris (Family Muraenidae)
Garden Eels
Splendid Garden Eels, Gorgasia preclara (Family Congridae)
American Eel
American Eel, Anguilla rostrata (Family Anguillidae)

(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
Silver Arowana, Osteoglossum bicirrhosum (Family Osteoglossidae)
Peter's Elephantfish, Gnathonemus petersii (Family Mormyridae)
African Knifefish, Xenomystus nigri (Family Notopteridae)

(Order Clupeiformes)

  • Shad, herring, sardines
  • Generalized bodies
  • Usually have silvery bodies
  • Lack lateral lines
  • ≈400 species; pelagic; feed on plankton
  • Many are commercially valuable
Northern Anchovies, Engraulis mordax (Family Engraulidae)
Pacific Sardines, Sardinops sagax (Family Clupeidae)
Knightia fossil
Knightia oecana fossil (Family Clupeidae); an extinct freshwater herring from the Eocene of WY (48 mya)

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
Common Carp, Cyprinus carpio (Family Cyprinidae), breeding aggregation; PA
Borneo Sucker
Robust Redhorse, Moxostoma robustum (Family Catostomidae)
Borneo Sucker
Borneo Sucker, Gastromyzon borneensis (Family Balitoridae)
Rosyside Dace
Rosyside Dace, Clinostomus funduloides (Family Cyprinidae)
White Cloud Mountain Minnow
White Cloud Mountain Minnow, Tanichthys albonubes (Family Cyprinidae)

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
African Red-eyed Tetra, Arnoldichthys spilopterus (Family Alestidae)
Common Hatchetfish, Gasteropelecus sternicla (Family Gasteropelecidae)
Pristella Tetra
Pristella Tetra, Pristella maxillaris (Family Characidae)
Neon Tetra
Neon Tetra, Paracheirodon innesi (Family Characidae)
Red-bellied Piranha, Pygocentrus nattereri (Family Serrasalmidae)
Payara, Hydrolycus scomberoides (Family Cynodontidae)

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
Channel Catfish
Channel Catfish, Ictalurus punctatus (Family Ictaluridae)
Sailfin Pleco
Amazon Sailfin Pleco, Pterygoplichthys pardalis (Family Loricariidae)
Three-lined Cory
Three-lined Cory, Corydoras trilineatus (Family Callichthyidae)
Shovel-nosed Catfish
Shovel-nosed Catfish, Sorubim lima (Family Pimelodidae)
Glass Catfish
Glass Catfish, Kryptopterus bicirrhis (Family Siluridae)
Electric Catfish
Electric Catfish, Malapterurus electricus (Family Malapteruridae)

(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
Electric Eel
Electric Eel, Electrophorus electricus (Family Electrophoridae)

Order Salmoniformes

  • Salmon & trout
  • Mostly fairly large size
  • Scales usually very fine
  • 223 species; in northern hemisphere rivers (some anadramous)
  • Some species commercially valuable
Chinook Salmon
Chinook Salmon, Oncorhynchus tshawytscha (Family Salmonidae)
Brook Trout
Brook Trout, Salvelinus fontinalis (Family Salmonidae)
Brown Trout
Brown Trout, Salmo trutta (Family Salmonidae)

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
Blackeye Goby
Blackeye Goby, Rhinogobiops nicholsii (Family Gobiidae)
Zebra Goby
Zebra Goby, Lythrypnus zebra (Family Gobiidae)
Firefish Goby
Firefish Goby, Nemateleotris magnifica (Family Microdesmidae)

(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
Rainbow Seaperch, Hypsurus caryi (Family Embiotocidae)
Yellow-headed Jawfish, Opistognathus aurifrons (Family Opistognathidae)
False Clown Anemonefish, Amphiprion ocellaris sp. (Family Pomacentridae)


  • 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
Angelfish, Pterophyllum scalare (Family Cichlidae)
Redfin Cichlid
Redfin Cichlid, Copadichromis borleyi (Family Cichlidae; from Lake Malawi)
Blue Lumphead
Blue Lumphead, Cyrtocara moorii (Family Cichlidae; from Lake Malawi)

(Order Atheriniformes)

  • Silversides & Rainbow fishes
  • Elongated, streamlined fishes
  • Silvery to colorful
  • Reduced lateral line
  • Rivers and brackish coastal waters
  • ≈350 species
Topsmelt, Atherinops affinis (Family Atherinopsidae)
Aussie Rainbowfish
Australian Rainbowfish, Melanotaenia fluviatilis (Family Melanotaeniidae)
Madagascar Rainbowfish
Madagascar Rainbowfish, Bedotia geayi (Family Bedotiidae)

(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
Garfish specimen
Needle-nosed Garfish, Xenentodon cancila (Family Belonidae), preserved specimen
Flying Fish specimen
Flying Fish, Cypselurus sp. (Family Exocoetidae), preserved specimen

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
Black Molly, Poecilia sphenops (Family Poeciliidae)
Western Mosquitofish, Gambusia affinis, male (Family Poeciliidae); note Gonopodium
Striped Panchax
Striped Panchax, Aplocheilus lineatus (Family Aplocheilidae)
Gila Topminnow
Gila Topminnow, Poeciliopsis occidentalis (Family Poeciliidae); an endangered species native to AZ
Desert Pupfish
Desert Pupfish, Cyprinodon macularius (Family Cyprinodontidae); an endangered species native to AZ
Foureye Fish
Large-scaled Four-eye Fish, Anableps anableps (Family Anablepidae)

(Order Carangiformes)

  • Jacks, etc.
  • Streamlined shapes
  • Carangiform swimming, with sickle-shaped caudal fin
  • Generally silver in color
  • Fast-swimming pelagic marine fish
  • 160 species
Rainbow Runners
Rainbow Runners, Elagatis bipinnulata (Family Carangidae)
Lookdown, Selene vomer (Family Carangidae)
Dolphinfish (or Mahi Mahi), Coryphaena hippurus (Family Coryphaenidae)

(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
Dwarf Gourami
Dwarf Gourami, Colisa lalia (Family Osphronemidae)
Opaline Gourami
Opaline Gourami, Trichogaster microlepis (Family Osphronemidae)
Leopard Bushfish
Leopard Bushfish, Ctenopoma acutirostre (Family Anabantidae)

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
Starry Flounder
Starry Flounder, Platichthys stellatus (Family Pleuronectidae)
Sanddab, Citharichthys sp. (Family Paralichthyidae)
Fantailed Sole
Fan-tailed Sole, Xystreurys liolepis (Family Bothidae)

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
Pacific Seahorse, Hippocampus ingens (Family Syngnathidae)
Sea Dragon
Leafy Sea Dragon, Phycodurus eques (Family Syngnathidae)
Chinese Trumpetfish, Aulostomus chinensis (Family Aulostomidae)
Yellow-banded Pipefish
Yellow-banded Pipefish, Syngnathoides biaculeatus (Family Syngnathidae)
Longspine Snipefish, Macroramphosus scolopax (Family Centriscidae)
Long-tailed Seamoth, Pegasus volitans (Family Pegasidae)

(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
Pacific Mackerel, Scombus japonicus (Family Scombridae)
Bluefin Tuna
Pacific Bluefin Tuna, Thunnus orientalis (Family Scombridae)
Pacific Pompano, Peprilus similimus (Family Stromateidae)

(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
Harlequin Tuskfish, Choerodon fasciatus (Family Labridae)
Cleaner Wrasse
Cleaner Wrasse, Labroides dimidiatus (Family Labridae); an important reef mutualist
Bird Wrasse
Bird Wrasse, Gomphosus varius, male (Family Labridae)

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
Redbreasted Sunfish
Red-breasted Sunfish, Lepomis auritus (Family Centrarchidae)
Cherokee Darter, Etheostoma scotti (Family Percidae)
Common Snook, Centropomus undecimalis (Family Centropomidae)
Clarion Angelfish
Clarion Angelfish, Holacanthus clarionensis (Family Pomacanthidae)
Porkfish, Anisotremus virginicus (Family Haemulidae)
Potato Grouper
Potato Grouper, Epinephelus tukula (Family Serranidae)

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
Lionfish, Pterois sp. (Family Scorpaenidae)
Stone Scorpionfish
Stone Scorpionfish, Scorpaena mystes (Family Scorpaenidae)
Lumptail Sea-Robin
Bighead Sea-Robin, Prionotus tribulus (Family Triglidae)
China Rockfish
China Rockfish, Sebastes nebulosus (Family Scorpaenidae)
Three-spined Stickleback, Gasterosteus aculeatus (Family Gasterosteidae)
Grunt Sculpin
Grunt Sculpin, Rhamphocottus richardsoni (Family Cottidae)

(Order Spariformes)

  • Breams & Porgies
  • Small to medium size
  • Mostly united by molecular data
  • ≈300 marine & brackish waters
Two-lined Monocle Bream, Scolopsis bilineata (Family Nemipteridae)

(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
Frogfish, Antennarius sp. (Family Antennariidae)
Pacific Footballfish, Himantolophus sagamius, preserved specimen (Family Himantolophidae)
Cabrillo Marine Aquarium

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
Pacific Boxfish
Pacific Boxfish, Ostracion meleagris (Family Ostraciidae)
Figure-8 Puffer, Tetraodon biocellatus (Family Tetraodontidae)
Scrawled Filefish
Scrawled Filefish, Aluterus scriptus (Family Monacanthidae)
Scrawled Cowfish
Scrawled Cowfish, Acanthostracion quadricornis (Family Ostraciidae)
Picasso Triggerfish
Picasso Triggerfish, Rhinecanthus aculeatus (Family Balistidae)
Ocean Sunfish
Ocean Sunfish, Mola mola (Family Molidae)
This is the heaviest bony fish, weighing up to 1 ton.
This page last updated 12 July 2017 by Udo M. Savalli ()
Images and text © Udo M. Savalli. All rights reserved.