Origin of Tetrapods

Question 1

Which group of fishes did tetrapods originate from?

Answer 1

Lobe finned fishes - sarcopterygians

Question 2

What characteristics does Eusthenopteron share with tetrapods?

Answer 2

Internal nostrils, lungs and gills, limbs with bony axis, labyrinthodont teeth, skull pattern

Question 3

Which early amphibian did Eusthenopteron coexist with?

Answer 3

Elpistostege

Question 4

Was Eusthenopteron a tetrapod?

Answer 4

No, it was definitely a fish but a close relative of early tetrapods

Question 5

What was the crucial transition state fossil between Eusthenopteron and the early tetrapods Acanthostega and Ichthyostega?

Answer 5

Tiktaalik rosae

Question 6

What did the head of Tiktaalik resemble?

Answer 6

A crocodile. Had a flattened head and eyes on top

Question 7

What features of Tiktaalik were fish-like?

Answer 7

It had caudal fins and no toes, gills, scales/fin rays

Question 8

What features of Tiktaalik were like a tetrapod?

Answer 8

Ribs, neck, and lungs

Question 9

What features of Tiktaalik were like a “fishapod”?

Answer 9

Limb bones and joints

Question 10

What skeletal modifications did Tiktaalik have compared to Eusthenopteron?

Answer 10

Pectoral girdle: has wrists, shoulders, elbows, and a neck

Rib cage: well developed and could probably move on land for short periods of time