Unit 10

Question 1

Why terrestrial animals?

Answer 1

Xeric environment
Predation
No land competition
Lots of food (insects)
Low O2 in stagnant pools
Dispersal between pools
Basking for temperature regulation

Question 2

Adaptions to shallow water life

Answer 2

Limbs with digits
Ankle and wrist development
Pelvic girdle attachment 
Bony operculum reduced
Longer flatter snout developed
—> extant fish similar adaptations

Question 3

Tetrapod origin

Answer 3

Tetrapodomorphs

Sarcopterygii —> Rhipdistia
- Dipnoi, Osteolepiforms, Elpistostegidae, Tetrapoda

Question 4

Osteolepiforms

Answer 4

Paired crescentic vertebrae
Teeth with labyrinthine enamel
E.g Eusthenopteron

Question 5

Elpistostegidae

Answer 5

Eyes on top of head
Dorsal and anal fin reduction
Tail fin reduction
Dorsoventrally flattened
Derived humerus
E.g. Panderichthys

Question 6

Tiktaalik Tetrapod features:

Answer 6

Loss of bony operculum
Ribs large and overlapping
Finger-like bones at end of fin

Question 7

Tiktaalik fish-like features

Answer 7

Gills
Poorly ossified vertebrae
Long body

Question 8

Early tetrapods

Answer 8

Acanthostega - primitive and aquatic
Ichthyostega
-Both aquatic and terrestrial
-Lumbar and thoracic regions
-Long ribs

Question 9

Early tetrapod characteristics

Answer 9

Primarily aquatic
Internal fishlike gills
Likely had lungs
Polydactyl (>5 toes)
Loved fins (locomotion)
Large body size
Soft operculum 
Less scales (maybe skin gas exchange)

Question 10

Non-amniotic tetrapods

Answer 10

Stem amphibians (batrachomorphs)
Stem amniotes (reptilomorphs)
Leposondyls

Question 11

Stem amphibians

Answer 11

Batrachomorphs
Temnospondyls
Frog and salamander ancestor
Aquatic, flat skulled, 4 digits

Question 12

Stem amniotes

Answer 12

Reptilomorphs
Anthracosaurs
Seymouria (larval form)
Diadectes - sister group to amniotes, large herbivorous teeth
Terrestrial, domed skull, 5 digits

Question 13

Lepospondyls

Answer 13

Caecilian ancestor?

Adapted to burrowing and aquatic movement

Question 14

Features of amniotes

Answer 14

Thicker, more waterproof skin
Costal ventilation (rib-ventilation of lungs)
Amniotic egg
Temporal fenestration of amniotes

Question 15

Amniotic egg

Answer 15

Membranes: chorion, amnion, allantois
No need to lay eggs in water
Embryonic membranes in egg homologous to placenta
Unknown reason for evolution
Internal fertilization —> copulatory organ developed

Question 16

Skull fenestrations

Answer 16

Synapsids
Sauropsids - secondary aquatic amniotes
Parareptiles - Pareiasaurs (dominant herbivore, Permian)
Eureptiles - early diapsids, early Permian, late Carboniferous

Question 17

Fenestrations

Answer 17

Adductor muscle attachment
-adductor mandibularis
Inertial feeding vs static feeding