Comparative Anatomy Vertebrate Phylogeny: Fishes Kardong Chapter s 2 & 3 Part 4

Vertebrate Classification Geological Eras of early vertebrates Geological Eras of early vertebrates Paleozoic (oldest) – see figure 4.1b Paleozoic (oldest) – see figure 4.1b Mesozoic Mesozoic Cenozoic Cenozoic Figure 4.1a

Figure 4.1b.

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

Chordate Origins: Lower to Higher Organisms Echinoderm ancestor (deuterostomes) gave rise to vertebrates Echinoderm ancestor (deuterostomes) gave rise to vertebrates Deuterostomes- blastopore gives rise to anus Deuterostomes- blastopore gives rise to anus Protostomes- blastopore gives rise to mouth Protostomes- blastopore gives rise to mouth Figure 4.3. (above) protostomes and (b) deuterostomes.

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

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

Placoderms Anadromous- fish move to freshwater to breed Anadromous- fish move to freshwater to breed Catadromous- fish move from freshwater to breed Catadromous- fish move from freshwater to breed Hypothesized function of bone: to provide calcium for muscle contraction Hypothesized function of bone: to provide calcium for muscle contraction Figure 4.7. Craniates through geological time (Book figure 3.1).

Cartilagenous Fishes Chondrichthyes Chondrichthyes Cartilaginous skeleton Cartilaginous skeleton Bone remains in scales - placoid scales Bone remains in scales - placoid scales Teeth are modified scales Teeth are modified scales Ex: elasmobranchs (sharks, rays = skates,) and the holocephalans (chimaeras-ratfishes) Ex: elasmobranchs (sharks, rays = skates,) and the holocephalans (chimaeras-ratfishes) Figure 4.8. Basking shark-second largest fish.

Elasmobranchii vs Holocephali Figure 4.9. (Book figure 3.13).

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

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

Evolutionary relationship of vertebrates with jaws (Gnathostomata) to those with bony skeleton (Osteichthyes ) Evolutionary relationship of vertebrates with jaws (Gnathostomata) to those with bony skeleton (Osteichthyes ) Figure 4.12.

Class Osteichthyes (cont.) Subclass Sarcopterygii (fleshy or lobe finned) Subclass Sarcopterygii (fleshy or lobe finned) 3 genera of lungfish are found on 3 separate continents 3 genera of lungfish are found on 3 separate continents Continental Drift Continental Drift Torpidity- inactivity; hibernation Torpidity- inactivity; hibernation Aestivation- burrow through dry season Aestivation- burrow through dry season Order Dipnoi Order Dipnoi Order Crossospterygii Order Crossospterygii Figure Aestivation; fish burrows into mud until rain returns. (see Box Figure 1, p. 101).

Early Sarcopterygians Figure Early Devonian fishes, including the newly described Tiktaalik (an intermediate link between fishes and land vertebrates). (Book figure 3.20.).

Order Crossopterygii “Living fossil fish” “Living fossil fish” Species thought to be extinct until coelacanth (Latimeria) discovered. Species thought to be extinct until coelacanth (Latimeria) discovered. Found off coast of South Africa in 1938 Found off coast of South Africa in 1938 May be a separate species discovered off Indonesia in 1999 May be a separate species discovered off Indonesia in 1999 Figure Global locations of coelacanth discoveries.

Coelacanth Figure Coelacanth in Indian Ocean.

Coelacanth Figure Africa’s Sundaytimes-political humor. Figure Coelacanth.

Crossopterygiians (lobe-finned fish) gave rise to labyrinthodonts (early tetrapods) in Devonian Period Figure Labyrinthodont (primitive tetrapod).

Linking Morphology Limbs Limbs Vertebrae Vertebrae Girdles similar Girdles similar Fins’ skeletal composition exhibits homology with early tetrapods Fins’ skeletal composition exhibits homology with early tetrapods Amphibian diversity during Carboniferous period Amphibian diversity during Carboniferous period Toward reptiles, Anura, Caudata, and Apoda. Toward reptiles, Anura, Caudata, and Apoda. Figure Figure 4.21.

More Linking Evidence Skulls – flattened with homologous bones Skulls – flattened with homologous bones A chiridium – muscular limb with well-defined joints and digits A chiridium – muscular limb with well-defined joints and digits Parietal foramen Parietal foramen Crossopterygian skull shows place for third eye Crossopterygian skull shows place for third eye Third (pineal) eye visible in young reptiles (e.g., tautara) Third (pineal) eye visible in young reptiles (e.g., tautara) Tooth structure Tooth structure Labyrinthodont tooth Labyrinthodont tooth Figure Crossopterygian skull. Figure Grooved tooth.

Lissamphibia – Modern Amphibians Apoda - caecilians Apoda - caecilians Long and slim; segmented rings Long and slim; segmented rings Dermal bones (scales) embedded in annuli Dermal bones (scales) embedded in annuli Figure Caecilian showing annular body rings.