Lecture 8 - 2.0

Question 1

What Had to be Changed from Water to Land (Tetrapods) (4):

Answer 1

1. Movement
2. Respiration
3. Sensing the environment
4. Feeding and reproduction

Question 2

What is a Tetrapod:

Answer 2

Vertebrates that possess a chiridium

Question 3

What is a Chiridium:

Answer 3

Muscular limb with well-defined joints and digits

Question 4

What Adaptations did the Tiktaalik Have (3):

Answer 4

1. Limb-like pectoral fins for support while standing and functional wrist joint
2. Mobile neck allowing flexible head movement
3. No bony gill covering suggested increased use of lungs for respiration

Question 5

What Adaptations Did the Acanthostega Have (2):

Answer 5

1. Limbs have digits (8 fingers, 8 toes)
2. Girdles are designed to bear weight (reinforced pelvic girdle)

Question 6

What Adaptations Did the Ichthyostega Have (2):

Answer 6

1. Limbs have digits (7 fingers and toes)
2. Lacked internal gills

Question 7

What Adaptations Did the Temnospondyls Have (2):

Answer 7

1. Robust bodies with flat skulls
2. Fossils known from larval stage where they go through metamorphosis

Question 8

What Adaptations Did the Lepospondyls Have (2):

Answer 8

1. Eel/Snake-like forms are aquatic
2. Lizard/newt-like forms are more terrestrial

Question 9

What are the Seven Major Changes from Fishes to Tetrapods:

Answer 9

1. Fins become Chiridium
2. Fused shoulders become a ‘True’ Neck
3. Reinforced vertebral column and girdles
4. Skull shortening and lost Hyomandibula attachment
5. Snout elongation and eye location
6. Reduction of skull bone pattern
7. Integument modifications

Question 10

1. What Does the Change from Fin Becoming Chiridium Entail (4):

Answer 10

1. Chirdium: muscular limb with well-defined joints and digits
2. Elements distal to base of fin expand in Rhipidistian fish
3. Modified to bear digits
4. Change in angle between humerus and radius/ulna

Question 11

2. What Does the Change from Fused Shoulder Becomes a ‘True’ Neck Entail (3):

Answer 11

1. Loss of bone covering gill chamber (operculum) in fishes
2. Loss of bones that joined the shoulder to back of skull roof in fishes
3. Evolution of the atlas vertebra (first cervical vertebra)

Question 12

3. What Does a Change to Vertebrae Entail (2):

Answer 12

1. Centra - becomes more ossified
2. Zygopophyses - appear so that the vertebral column can help keep the body off the ground.

Question 13

3. What Does the Change to Girdles Entail (3):

Answer 13

1. Changes in bones supporting the appendages (fish to tetrapod)
2. Physical connection with vertebral column for both girdles
3. Points of attachment for muscles used in new mode of locomotion.

Question 14

4. What Does the Skull Shortening and Lost Hyomandibula Attachment Entail (4):

Answer 14

1. Back part of the skull is shortened
2. Hyomandibula is no longer attached to the otic capsule (‘nose’)
3. Hyomandibula becomes stapes (‘ear’)
4. Braincase now supported by connection with roof of mouth

Question 15

5. What Does the Snout Elongation and Eye Location Entail (1):

Answer 15

Eyes move on top of head

Question 16

6. What Does the Reduction of Skull Bone Pattern Entail (2):

Answer 16

1. Fusion of small bones in nasal region (anterior)
2. Loss of bones in opercular region (posterior)

Question 17

7. What Does the Integument Modifications Entail (2):

Answer 17

1. Dermal scales of fish were modified into scutes or gastralia
2. Cover only the belly in Tetrapods

Question 18

How did Early Tetrapods Move:

Answer 18

• Limbs and girdles were too small and poorly ossified for walking on land
• Limbs likely used as points of pivot to support lateral flexion of the body in shallow water, as proposed for lobe-finned fishes