Fishes Families/Classifications

Agnathans

• Jawless fishes

• Includes Myxiniformes (hagfish) and Petromyzontiformes (lampreys)

• Not monophyletic

• Anguilliform bodies

• Scaleless

• Absent paired fins

• Protocercal caudal fin

• No vertebrate; has a notochord as supporting structure

• Single median nostril

Myxinidae

• Includes hagfishes

• Barbels around mouth and horny plates

• Reductive fin folds

• Secretes copious amount of mucus

• Hermaphroditic

• Lives in deeper, ocean enviroments

• Scavengers

Petromyzontidae

• Includes lampreys

• Suctorial mouth with no barbels

• Euryhaline and anadromous

• Some species are restricted to freshwater

• Parasitic

Chondrichthyes

• Cartilaginous fishes; skeleton is made of cartilage

• Includes Holocephali (chimeras, ratfishes) and Elasmobranchii (sharks, rays, skates)

• Placoid scales

• Electrosensory system

• Internal fertilization

• Sister group of the bony fish clade Teleostomi

Holocephali

• Includes chimeras and ratfishes

• Has a single external gill opening

• No caudal fin

• Teeth crushing plates

• Most are scaleless

Elasmobranchii

• Includes sharks, rays, and skates

• Has multiple gill slits

• Spiracles are usually present

• Multiserial replacement detention

• Palatoquadrate not fused to cranium

• Caudal fin heterocercal

Carcharhiniformes

• Largest order of sharks (~300 spp.)

• Includes the families:

  • Carcharhinidae (requiem sharks)

  • Sphyrnidae (hammerheads)

Lamniformes

• Includes mackerel sharks (great whites, shortfin mako, etc.)

• Includes the family Lamnidae (mackerel sharks)

• Endothermic

Squaliformes

• Order of 130+ spp. of sharks

• Includes the family Squalidae (dogfish sharks)

• Anal fin absent

• Large spiracle present

• Some spp. form large schools

Batoidea

• Suborder that includes skates, rays, and guitarfishes

• Depressiform

• Enlarged pectoral fins

• Spiracle is large

• Gill openings are on ventral side

Rajiformes

• Includes the families:

  • Rhinidae (guitarfishes)

  • Rajidae (skates)

• Dorsal thorn-like spines

Dasyatidae

• Family of fishes that includes stingrays

• Whip-like tail; no caudal fin

• Serrated venomous spine

Osteichthyes

• Bony fishes; skeleton made of bone

• Fin rays are at least partially ossified

• Bas bladder is present

• Divided into 2 main clades:

  • Sarcopterygii

  • Actinopterygii

Sarcopterygii

• Lobe-finned fishes

• Intracranial joint

• Modified ceratotrichia (fin rays)

• Cosmoid scales

• Choanae (internal nostrils) present in some

Coelacanthiformes

• Includes coelacanths

• Under Sarcopterygii

• Three-lobed diphycercal caudal fin

• Choanae absent

• Fin rays not branched

• Unconstriced unossified notochord

• Intracranial joint

• Most fins are lobed

Dipnoi

• Includes lungfishes

• Under Sarcopterygii

• Diphycercal caudal fin

• Plate-like teeth

• Palatoquadrate fused with cranium (no premaxilla)

• Gas bladder used in air breathing

• Includes two orders:

  • Ceratodontiformes

  • Lepidosireniformes

Ceratodontiformes

• Includes the Australian lungfish

• Single gas bladder

• Facultative air breather (optional air breather)

• Flipper-like paired fins

Lepidosireniformes

• Includes the African and South American lungfish

• Two gas bladders

• Obligate air breather (gills did not fully form)

• Paired fins filamentous

• Estivate (hibernation-like state) in mud during dry season