Tetrapod Evolution

Question 1

When did the Tetrapods evolve ?

Answer 1

The Devonian Period, 359-416 million years ago.

Question 2

What is the tetrapods sister clade ?

Answer 2

Lobbed finned fishes

Question 3

Give the key features of the tetrapods

Answer 3

Have limbs, not paired fins
Ankle and wrist joints
Fully developed pectoral girdle
Distinct humerus (arm bone)

Question 4

Give the early ancestors of the Tetrapods, beginning with Eusthenopteron

Which of these extant species is found in the tetrapod group ?

Answer 4

Eusthenopteron
Panderichythys
Tiktaalik
Acanthostega (Tetrapod)
Icthyostega (tetrapod)

Question 5

What are the stegocephalians ?

Answer 5

Early non fish vertebrates
4 limbed, with digits not fins
‘Roofed head’ Stega Cephalia

Question 6

In which extinct species did the first evidence of the humerus, radius and ulna appear ?

Answer 6

Eusthenopteron

Question 7

Give the key adaptions of the Panderichythys.

Answer 7

Able to occupy land and marine, Shallow habitats.
Dorsoventrally flattened
Fins with radial bones.

Question 8

Why is tiktaalik important ?

Answer 8

It is the intermediate species between fish and modern amphibians

Question 9

Give the fish characteristics of tiktaalik.

Answer 9

Scales, fins, gills, lungs

Question 10

Give the tetrapod charecterstics of Tiktaalik

Answer 10

Eyes on top of skull. neck, ribs, fin skeleton.

Question 11

Acanthostega and Icthyostega share common characteristics, which include…

Answer 11

Both carnivores
4 limbs with well developed digits (unsure of function)
alternating symmetrical gait

Question 12

What is the importance of CT scans for these transition fossils ?

Answer 12

Enable model reconstructions.

Can deduce limb angles and therefore behaviour od that organism