1. KINGDOM ANIMALIA Phylum Chordata Subphylum Vertebrata Superclass Osteichthyes

2. Vertebrate Classes

3. Class Actinopterygii Ray-finned fishes
Most bony fishes and largest single group of chordates (24,000 species)
Well-adapted; successful in marine and freshwater
Carnivores, herbivores, parasites, and scavengers

4. Features Well-developed lateral fins
Fins contain delicate bony rays extending from internal skeleton
Provide support and articulation
Caudal fin provides thrust and other fins stabilize

5. Features Scales = light bone (small or absent in fast swimmers)
Swim bladder (lung)
saclike extension of digestive tract during development
used to retain gases to provide fish with buoyancy (don’t sink, energy saving)
may also be used for atmospheric respiration
Gills to maximize area for gas exchange
Covered by bony operculum
Force water over gills when not moving

6. Features Acrodin-covered teeth Circulation Brain 2-chambered heart
Blood flow under low pressure
Blood flows in opposite direction as water in gills, which maximizes oxygen saturation
Brain
Sensory and to some extent motor coordinating centers well developed
Overall coordinating and reasoning centers are primitive

7. Examples
Primitive: heavy scales, use swim bladder for respiration in stagnant waters
Bichir - freshwater Africa
Gar - Kansas
Paddlefish - N. Am.
Sturgeon - N. Am.
Bowfin - N. Am.

8. Examples
Derived: Dominant fishes today; extremely diverse (morphology); upper jaw protrusible, thin/flexible scales, swim bladder for buoyancy
Herring (predator)
Coral reef fish (lateral compression)
Flounder (very laterally compressed, swim on side, eyes on upper body)
Moray eel (tubular, sacrifice speed for agility)

9. Class Actinistia
Only one marine species remains in this ancient lineage
Lobe-finned fish called a coelacanth
Only living chordate with a movable intracranial joint
divides skull into anterior and posterior halves
may allow upper jaw to elevate
Fatty swim bladder
(some buoyancy)
Predator
Enamel-covered teeth

10. Coelacanth
Thought to have been extinct until discovery in Indian Ocean in 1938
Since then, recovered 70+
Live in underwater lava caves at depths of meters
Compared to fossil evidence, not many changes-habitat stable (molecular level unknown)

11. Class Dipnoi Lobe-finned fishes Reduced skeleton
Teeth modified into plates (enamel)
Intracranial joint is immobile
Swim bladder highly vascularized and used as a lung

12. Lungfishes
6 species of freshwater lungfishes found in tropical regions of Africa, Australia, and S. America
Areas subject to drought
Some use lungs when conditions unfavorable, use gills otherwise
In others, gills reduced and dependent on lungs

13. African Lungfish Burrows in mud when water dries up
Secretes a mucous cocoon around its body with air hole at tip
Can survive up to 4 years

15. Tetrapod Ancestors
Response to periodic drying or to avoid predation/competition in aquatic habitat
Limbs further developed as stayed on land
Few competitors, no predators—selective pressure in favor of the land move
2 features:
Functional lungs (as well as gills)
Fleshy lateral fins containing muscle to support body and provide mobility

16. Tetrapod Ancestors
Skeletal bones in fins similar to bones of primitive tetrapods
Limbs thought to have developed in the water, not on land