Lecture 3

Question 1

List the five classes of fish, give examples and characteristics

Answer 1

-Agnatha (Cyclostomata vs Ostracodermi)

-Acanthodii (Climatius)
• Streamlined body
• Lack of large dermal scales:
• Ganoid type
• Numerous paired and unpaired
spines
• Most were freshwater, but early
forms were marine.

- Placodermi (Arthrodira)
• Head and trunk armor
• Streamlined body
• Paired pectoral and pelvic
fins
• Active swimmers and
predators
• Some were very large (up to 30 ft
in length).
• Movable joint between head
shield and trunk.

-Chondrichthyes (Elasmobranchii: Sharks, ray skates)
Large-yolked eggs
• Upper jaw is hyostylic
• Paired double nostrils
• Gills open directly to exterior
• Spiracle in some forms
• Skeleton entirely of cartilage
• Males possess claspers on pelvic
fins to facilitate sperm transfer

-Osteichthyes (Sarcopterygii vs Actinopterygii)

Question 2

Compare ostracodermi with cyclostomata

Answer 2

Ostracodermi (Anapsids)

- Lacked jaws and paired appendages
- Pharyngeal pumping station
- Pineal organ
- Nasal openings
- 10 pairs of cranial nerves
- Dermal armor
- Bottom feeders

Cyclostomata (Lampreys)

- Lacked jaws and paired appendages
- Filter feeder (larva) freshwater environment
- Gills in pouches
- Adults are predaceous, spend most time in marine environment
- This lifestyle is referred to as anadromous

Question 3

List the 3 major developments that set gnathostomes apart from earlier fish

Answer 3

• Development of jaws
  
  • food ingested in morsels, presence of stomach allows for storage of food
• Paired appendages
  
  • Improved ability to pursue/escape
• Buoyancy mechanism
  
  • Evolved in the form of lungs and swim bladder
  • Fishes could control depth in water without having to swim continually
• (Note sharks must swim to control depth and lack swim bladders)

Question 4

List the major anatomical characteristic that distinguishes sarcopterygians from actinopterygians

Answer 4

Sarco = Lobed paired fins
• Internal fin skeleton is made of
cartilage or bone, not spines

Actino = Ray-finned fish
• Internal fin skeleton is made of
spines.

Question 5

Which paleozoic era did fish first appear?

Answer 5

Cambrian

Question 6

Describe the significance of the 3 major morphological developments in gnathostomes

Answer 6

Early gnathostomes evolved two major anatomical advantages:
Jaws - utilize larger food items, presence of stomach for food storage
Paired appendages - allowed greater maneuverability in the water
Lungs and swim bladders - increase buoyancy