Characteristic of Early-Modern Fishes

· Ostracoderm

· Placoderm

· Acantodians

· Chondrochthyes

o Elasmobranch

o Holocephalii

o Cladoselachians

· Osteichthyes

o Crossopterygii

o Dipneusti

o Branchiopterygii

o Actinopterygii

§ Chondroteans

§ Neopterygii

· Holostei

· Teleotei

Ostracoderm

• jaws absent
• paired fin
• armored
• endoskeleton - cartilage
• caudal heterocercal
• small in size
• bottom dweller

Placoderm

• body covered with dermal plate
• internal skeleton present
• paired fin
• jaw present
• body dorsoventrally compressed

Acanthodian

• earliest jawed vertebrates in freshwater
• 'spiky sharks'
• bony+cartilaginous fish
• small
• large eyes
• streamlined body
• hard gonoid scales
• paired fins + spines

Chondrochthyes

• cartilage fish
• teeth present
• paired fin
• swim bladder
• valve spiral
• clasper (male)
• osmoregulation - urea
  

1. Elasmobranch (Sharks, Rays, Skates)
2. Holocephalii (Chimera)
   
3. Cladoselachians

- Elasmobranch

• predator
• 5-7 gill openings
• scales - placoid
• upper jaw not connected to cranium
• lower jaw connected either amphistyolic/hyostylic

- Holocephalii

• 4 gill openings
• operculum present
• spiracle absent
• upper jaw connected to skull
• teeth flat plate
• scales absent
• clasper (male) at head & at pelvic fin

- Cladoselachians

• clasper absent
• skull/cranium elongated
• jaw amphistylic
• no anal fin
• paired fin triangular
• cladodont teeth

Osteichthyes

• bony skeletons
• stable cranial bows, rooted teeth
• head & pectoral girdles covered with bones
• inner ear contains otoliths
• have lung/swim bladder
• operculum

1. Dipneusti (lungfish)
   
2. Crosssopterygii (coelacanth)
3. Actinopterygii (rayed finned fish)
   
4. Brachiopterygii (bichir & reedfish)
   

- Dipneusti

• lung
• true bone
• scales hard
• gills present
• gills protected by operculum
• paired fins

- Crossopterygii

• pseudo tetrapods
• jaws connected to skull
• complex teeth structure with enamel
• 3 lobed tails
• hard armor-like scale

- Actinopterygii

• most have scales
• no spiracles (usually)

1. Chondostei (Sturgeon fish)
   
2. Neopterygii

**Chondostei

• freshwater
• scale ganoid
• spiracle
• caudal heterocercal
• skull has 3 connected strong bones

**Neopterygii

• sea & freshwater
• operculum 4 bones
• tail homocercal
• scales bony
• swim bladder reduced

1. Holostei
2. Teleostei

- Brachiopterygii (bichir & reedfish)

• spiracle single
• scales ganoid
• spinous dorsal finlets