1. Comparative Anatomy Vertebrate Classification Fish Evolution
Note Set 3
Chapter 3

2. Vertebrate Classification
Figure 4.1
Geological eras of early vertebrates
Paleozoic (oldest)
Mesozoic
Cenozoic

3. Cambrian Period Ostracoderms- first vertebrates, shell skinned
Class Agnatha- jawless fish
No paired fins
Bony exoskeleton with
dermal armor
Ex: hagfish and lampreys
Jawed fish evolved from Ostracoderms in Silurian period
(a)
(b)
Figure 4.2: (a) ostracoderm, (b) ostracoderm, and (c) lamprey.
(c)

4. Lower vs. Higher Organisms
Echinoderm-like organism (deuterostomes) gave rise to vertebrates
Deuterostomes- blastopore gives rise to anus
Protostomes- blastopore gives rise to mouth
(a)
(b)
Figure 4.3- (a) protostomes and (b) deuterostomes.

5. Placoderms Class Placodermii Jawed and paired fins
Bony dermal exoskeleton; armored fish
1st jaws were large
Jawed fishes gave rise to all other fishes
Age of fishes- Devonian Period
Figure 4.4- Armored fish
Figure 4.5- mandibular (ma) and hyoid (hy) arches
develop in gnathostomes into palatoquadrate (pq) and Meckel’s (Mc) cartilages

6. Fish Evolution
(a)
(b)
Figure 4.6: (a) jawless fish, (b) early jawed fish, and (c) modern jawed fish
(c)

7. Placoderms Anadromous- fish move to freshwater to breed
Catadromous- fish move from freshwater to breed
Hypothesized function of bone- to provide calcium for muscle contraction
Figure 4.7: Craniates through geological time.

8. Fish Chondrichthyes Cartilaginous skeleton
Bone remains in scales- placoid scales
Teeth are modified scales
Ex: sharks, rays, skates
Figure 4.8: Shark

9. Tail Type
Heterocercal- vertebral axis curves upward; two asymmetrical lobes (dorsal portion larger)
More primitive, some bony fish
Ex: sharks
Homocercal- symmetrical dorsal and ventral lobes
Most common
Ex: perch
Diphycercal- spear shaped
Ex: lungfish, crossepterygians
Figure 4.9

10. Class Osteichthyes Subclass Actinopterygii (ray-finned)
Chondrostei- most primitive; heterocercal tail
Ex: sturgeon, paddlefish, Polypterus
Holostei- dominant in past; heterocercal tail
Ex: gar, bowfin
Teleostei- dominant today; homocercal tail
Majority of all fish
Figure us lionfish (actinopterygian).

11. Figure 4.11
Evolutionary relationship of vertebrates with jaws (gnathostomata) to those with bony skeleton (osteichthyes)

12. Class Osteichthyes Subclass Sarcopterygii (fleshy or lobe finned)
3 genera of lungfish appeared on 3 separate continents
Continental Drift
Torpidity- inactivity; hibernation
Aestivation- burrow through dry season
Order Dipnoi
Order Crossopterygii
Figure 4.12: Aestivation; fish burrows into
mud until rain returns.

13. Order Crossopterygii Living fossil
Species thought to be extinct until coelacanth (Latimeria)
Found off coast of South Africa in 1938
Separate species discovered off Indonesia in 1999
Figure 4.13: Global locations of coelacanth discoveries.

14. Coelacanth
Figure 4.14: Coelacanth in Indian Ocean.

15. Coelacanth
Figure 4.15
Figure Africa’s Sunday Times.

16. Figure 4.17: Labyrinthodont
Crossopterygiians (lobe-finned fish) gave rise to Labyrinthodonts (early amphibians)
in Devonian Period

17. Linking Evidence Skulls Parietal foramen Tooth structure
Crossoterygii skull shows place for third eye
Third (pineal) eye visible in young tuatara reptiles
Tooth structure
Labyrinthodont tooth
Figure 4.18: Crossopterygii skull.
Figure 4.19: Grooved tooth.

18. Linking Evidence Limbs evolved Vertebrae Girdles similar
Fin’s skeletal composition exhibits homology with early amphibians
Amphibian diversity during Carboniferous period
Toward reptiles, Anura, Caudata, and Apoda
Figure 4.20
Figure 4.21

19. Amphibian Characteristics
1st to possess cervical vertebrae
Lost scales
Primitive frogs have dermal scales
Anamniotic eggs
3 chambered heart
Metamorphosis
10 pairs of cranial nerves
2 occipital condyles

20. Apoda Caecilians Long and slim; segmented rings
Dermal bones (scales) embedded in annuli
Figure 4.22

21. Literature Cited
Figure
Figure 4.2(a)-
Figure 4.2(b)-
Figure 4.2(c)-
Figure 4.3- Kardong, K. Vertebrates: Comparative Anatomy, Function, Evolution. McGraw Hill, 2002.
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Figure
Figure
Figure 4.7- Kent, George C. and Robert K. Carr. Comparative Anatomy of the Vertebrates. 9th ed. McGraw-Hill, 2001.
Figure
Figure
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Figure
Figure
Figure Gorr, Thomas and Traute Kleinschmidt. Evolutionary Relationships of the Coelacanth. American Scientist. Vol. 81, No. 1: Sigma Xi, 1993.
Figure 4.13 &115-
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