Comparative Anatomy
Vertebrate Classification
Fish Evolution
Note Set 3
Chapter 3
Vertebrate Classification
Figure 4.1

Geological eras of early
vertebrates



Paleozoic (oldest)
Mesozoic
Cenozoic
Cambrian Period


Ostracoderms- first vertebrates,
shell skinned
Class Agnatha- jawless fish
No paired fins
 Bony exoskeleton with
dermal armor
 Ex: hagfish and lampreys

(c)

(a)
(b)
Figure 4.2: (a) ostracoderm, (b) ostracoderm,
and (c) lamprey.
Jawed fish evolved from
Ostracoderms in Silurian period
Lower vs. Higher Organisms



Echinoderm-like
organism
(deuterostomes) gave rise
(a)
to vertebrates
Deuterostomesblastopore gives rise to
anus
Protostomes- blastopore
gives rise to mouth
(b)
Figure 4.3- (a) protostomes and (b) deuterostomes.
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
Fish Evolution
(a)
(b)
Figure 4.6: (a) jawless fish, (b)
early jawed fish, and (c) modern
(c)
jawed fish
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.
Fish

Chondrichthyes
Cartilaginous
skeleton
 Bone remains in
scales- placoid scales
 Teeth are modified
scales
 Ex: sharks, rays,
skates

Figure 4.8: Shark
Tail Type

Heterocercal- vertebral axis curves
upward; two asymmetrical lobes
(dorsal portion larger)



Homocercal- symmetrical dorsal and
ventral lobes



More primitive, some bony fish
Ex: sharks
Most common
Ex: perch
Diphycercal- spear shaped

Ex: lungfish, crossepterygians
Figure 4.9
Class Osteichthyes

Subclass Actinopterygii
(ray-finned)

Chondrostei- most primitive;
heterocercal tail


Holostei- dominant in past;
heterocercal tail


Ex: sturgeon, paddlefish,
Polypterus
Ex: gar, bowfin
Teleostei- dominant today;
homocercal tail

Majority of all fish
Figure 4.10- us lionfish (actinopterygian).
Figure 4.11

Evolutionary relationship of vertebrates with
jaws (gnathostomata) to those with bony
skeleton (osteichthyes)
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.
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.
Coelacanth
Figure 4.14: Coelacanth in Indian Ocean.
Coelacanth
Figure 4.15
Figure 4.16- Africa’s Sunday Times.
Figure 4.17: Labyrinthodont
Crossopterygiians (lobe-finned fish) gave rise to
Labyrinthodonts (early amphibians)
in Devonian Period
Linking Evidence


Skulls
Parietal foramen
Crossoterygii skull
shows place for third
eye
 Third (pineal) eye
visible in young
tuatara reptiles


Figure 4.18: Crossopterygii skull.
Tooth structure

Labyrinthodont tooth
Figure 4.19: Grooved tooth.
Linking Evidence





Limbs evolved
Vertebrae
Girdles similar
Fin’s skeletal
composition exhibits
homology with early
amphibians
Amphibian diversity
during Carboniferous
period

Figure 4.20
Toward reptiles, Anura,
Caudata, and Apoda
Figure 4.21
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
Apoda



Caecilians
Long and slim;
segmented rings
Dermal bones (scales)
embedded in annuli
Figure 4.22
Literature Cited
Figure 4.1- http://custance.org/Library/Volume2/Part_V/Chapter2.html
Figure 4.2(a)- http://www.alientravelguide.com/science/biology/life/ostracod.htm
Figure 4.2(b)- http://www.zoology.ubc.ca/courses/bio204/lab5_photos.htm
Figure 4.2(c)-http://www.ohiodnr.com/dnap/rivfish/ohiolamp.html
Figure 4.3- Kardong, K. Vertebrates: Comparative Anatomy, Function, Evolution. McGraw Hill, 2002.
Figure 4.4- http://www.ucmp.berkeley.edu/vertebrates/basalfish/placodermi.html
Figure 4.5- http://www.origins.tv/darwin/jaws.htm
Figure 4.6- http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookDiversity_9.html
Figure 4.7- Kent, George C. and Robert K. Carr. Comparative Anatomy of the Vertebrates. 9th ed.
McGraw-Hill, 2001.
Figure 4.8- http://www.bio.miami.edu/dana/106/106F04_17.html
Figure 4.9- http://departments.juniata.edu/biology/vertzoo/fish_lab.htm
Figure 4.10- http://www.anselm.edu/homepage/jpitocch/genbios/vertevol.html
Figure 4.11- http://www.geol.umd.edu/~jmerck/eltsite01/reading/eltsysex/sysq6.gif
Figure 4.12- http://malawicichlids.com/mw11001a.htm
Figure 4.14- Gorr, Thomas and Traute Kleinschmidt. Evolutionary Relationships of the Coelacanth.
American Scientist. Vol. 81, No. 1: Sigma Xi, 1993.
Figure 4.13 &115- http://news.bbc.co.uk/1/hi/sci/tech/302368.stm
Figure 4.16- http://www.suntimes.co.za/specialreports/zimbabwe/?MenuItem=s0
Figure 4.17- http://faculty.uca.edu/~benw/biol4402/lecture8c/img016.jpg
Figure 4.18- http://www.palaeos.com/Vertebrates/Units/140Sarcopterygii/140.400.html
Figure 4.19- http://www-biol.paisley.ac.uk/biomedia/gallery/labyrinthodont.htm
Figure 4.20- http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookDiversity_9.html
Figure 4.21- http://people.eku.edu/ritchisong/342notes1.htm
Figure 4.22- http://elib.cs.berkeley.edu/aw/lists/Caeciliidae.shtml