Question

The crossopterygians are an order of saurcopterygii which include the species Tiktaalik and Eusthenopteron. What is the evolutionary significance of these species?

Answer 1

Answer:-

Significance of Eusthenopteron:

Eusthenopteron, genus of extinct lobe-finned fishes (crossopterygians) preserved as fossils in rocks of the late Devonian Period (about 370 million years ago). Eusthenopteron was near the main line of evolution leading to the first terrestrial vertebrates, the tetrapods. It was 1.5 to 1.8 metres (5 to 6 feet) long and was an active carnivore, with numerous small teeth in its broad skull.

Significance of Tiktaalik:-

In many news articles, Tiktaalik was billed as "the missing link" between fish and land vertebrates — but that description is a bit misleading. First, Tiktaalik is more accurately described as a transitional form than a missing link. Transitional forms help show the evolutionary steps leading from one lineage to another by displaying characteristics of both the ancestral and the new lineage. These character suites help us understand the order in which the traits of the new lineage evolved and what functions they served as they evolved. Tiktaalik, for example, had fins with thin ray bones, scales, and gills like most fish. However, it also had the sturdy wrist bones, neck, shoulders, and thick ribs of a four-legged vertebrate. Tiktaalik was specialized for life in shallow water, propping itself up on the bottom and snapping up prey. The adaptations it had for this lifestyle ended up providing the stepping stones for vertebrates to climb onto dry land — but of course, Tiktaalik was not "aiming" to evolve features for land-living. Tiktaalik was simply well-adapted for its own lifestyle and later on, many of these features ended up being co-opted for a new terrestrial lifestyle.

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