1. Vertebrate Evolution and Diversity
Biology 351
Python vs. Alligator
Python consuming deer.

2. Vertebrate Evolution

3. First Step: Notochord is Replaced by Vertebrae

4. From jawless filter feeding chordate
Stem Vertebrate
From jawless filter feeding chordate
Ostracoderms
Stem vertebrate
Dermal bony armor
Jawless, filter feeder
No paired fins
Cephalization
Agnathans
Reduction in armor
Jawless fish
cyclostomes

5. Agnathans (jawless fish) –first vertebrates
Ostracoderms –armored jawless fish -extinct
most were filter feeders, may have been able to filter sand

6. Living Jawless Fish Hagfish Notochord with some skeletal plates
parasitize other fish

8. From Ostracoderm ancestor
Primitive Jawed Fish
Switch to predation
Jaws and teeth
Gills respiratory only
Decrease armor for speed
Increase sense organs
Paired fins
gave rise to all fish
Placoderms -extinct
Armor reduced (some to bony scales)
Paired fins
Cartilage skeleton
Some with claspers
May have given rise to Chondrichthyes -Cartilage Fish (sharks and rays)

9. Chondrichthyes (Cartilage Fish)
endoskeleton made of cartilage
most are fast predators and extremely agile
large sensory arrays (eyes, olfaction, taste, lateral line, magnetic sense)
gills individually exit oral cavity

10. Sharks and Rays
Silky shark
Great White
Blue Spotted Ray
Sting Ray

11. Primitive Osteichthyian
From Primitive Jawed Fish
Primitive Osteichthyian
Actinopterygii
Air bladder (accessory resp organ)
Bony skeleton
Decrease bony armor
Fin rays
bony scales
Ray Finned Fish
Connection from air bladder to pharynx lost in most (bouyancy)
Well developed fin rays
No internal nares
Gave rise to teleosts (modern bony fish)
Most have an operculum

12. Osteichthyes –bony fish

13. From Primitive Jawed Fish
Sacrcopterygian
Internal nares
Flesh lobed fins
Air bladder = lungs
Cosmoid scales
Dipnoi: Lungfish
Fin structure different from amhibians
Actinistia: Coelocanths
Rhipidistian
Deep sea rhipidistian
Bladder filled with fat
Sarcopterygian with improved pectoral and pelvic bone structure for walking on bottom; less fin rays

14. Fin Rayed vs. Flesh Lobed Fish

15. Lissamphibia From Flesh Lobed Fish (Sacrcopterygii Rhipidistian)
Labyrinthodont
Stem amphibian
Inwardly folded enamel teeth
Limbs with digits
Lateral line
First ear bones
Rayed tail
Some keratinized skin
Need water to reprod.
Flattened skull
Lissamphibia
Modern Amphibians
No scales
Thin keratinized skin
Gave rise to modern amphibians

16. Tiktaalik

17. Amphibians includes salamanders, newts and frogs
must return to water to mate and/or lay eggs

18. Cotylosaurs Diapsids Synapsids Archosaurs Lepidosaurs Aves: Birds
Stem reptile (anapsid)
amniotic egg
Keratinized scales
Skin impervious to water
Separate pulmonary
Ribs aid respiration and systemic circulation
Lateral movement of neck
Digits tipped with claws
Turtles
Carapace and plastron composed of bone and covered by scales
Anapsid skull
Highly mobile neck
Diapsids
Two temporal fenestrae
Improved erect posture
Gave rise to all other reptiles and birds
Synapsids
Single, lower temporal fenestra
Canine tooth
regulated body temperature
leads to mammals
Ex: dimetrodon
Lepidosaurs
Archosaurs
Dinosaurs and crocodilians
Aves: Birds
Lizards, snakes, and euryapsids
Homiothermic, feathers

19. Amniotic Egg extra-embryonic membranes
Amnion –bring pond to embryo
Yolk sac – food storage
Allantois –waste storage
Chorion –contact with ext. environment
hard outer shell impermeable to water
adapted for dry environment

20. Reptiles Adapted for Land amniotic egg scales more upright posture
hearing

21. Birds
descendents of Archosaurs
feathers
homeothermic

22. Synapsids Therapsids Mammal-like reptile Mammals Monotremes Eutherians
Enlarged canine teeth
More upright stance
Heterodonts
may have been homeothermic
Contained subgroup –Cynodonts
Had enlarged dentary bone
Back teeth with cusps
No lumbar ribs
Mammals
Endothermic
Three ear ossicles: mallus, incus and stapes
Large brain, Hair, Mammary glands
Monotremes
Eutherians
Lay eggs
No nipples
Echidna and platypus
Placental mammals with long gestations
Metatherians
Marsupials
Young born live but premature
Complete development in pouch attached to nipple

23. Mammals
mammary glands
hair
Egg-laying
Pouched
Placental