Question

Evolution of the Vertebrates Exercises 301 Latimeria, a modern sarcopterygian coelacanth living near Madagascar. Note the similarity of the tail to that of Eusthenopteron fossils in the previous figure. The tail is very different from that of the ray-finned fishes. This example is about 2 m long. (From Levin, H., 2013, The Earth Through Time (10 edition), figure 12-75, p. 370. This material is reproduced with permission of John Wiley & Sons, Inc.) 55. Compare the shape of the tail of the living coelacanth to that of Esthenopteron. Describe the similarities and differences 56. Compare the tail of the coelacanth to that of the ray-finned fishes from the Green River Formation. In the boxes below, sketch both and describe the differences. Tail of Coelucanth Tail of ray-finned fish 57. Describe the fusion swim bladder 58. Which type of fish was the most likely ancestor to the amphibians? Some of the best-preserved fossil fish are in the Green River Formation (Eocene) in Wyoming Ray-finned fishes (actinopterygians) from the Green River Formation (Eocene), Wyoming. The largest fish is about 25 cm long.

Answer 1

55.

Both living coelocanth and Eusthenopteron have trilobed tales.

Living coelocanth have trilobed, diphycercal tales wheras Eusthenopteron are lobe finned fish that have epicercal tail, have an upward tapering.

56.

Homoercal caudal fin Bulbous 3 lobed tail Coelocanth hay finned fish

Coelocanth tail pocess three lobes of fin (trilobed fin). The spinal cord extends to the end of its tail,therefore they have diphycercal tail.

The upper and lower lobes of ray finned fishes are in equal length (homocercal).

57. Swim bladder enables fishes to maintain it's depth without sinking.

It ia flexible gas-filled sacs that helps the fish to adjust buoyancy. It is hydrostatic organ derived from digestive tube's outpocketing and is located in body cavity.

58. Amphibians evolved from sacropterygian lobe-finned fishes.

I.e, lung fishes with bony-limbed fins. Presence of lungs and bony-limbs were helpful to survive in land. The nearest relative of amphibians among sacropterygians are osteolepiformes.