Who is Tiktaalik roseae? Why is it important? In what sense is it a transitional form (describe it’s characteristics).
One of the greatest fulfilled predictions of evolutionary biology is the discovery, in 2004, of a transitional form between fish and amphibians. This is the fossil species Tiktaalik roseae, which tells us a lot about how vertebrates came to live on the land.
Tiktaalik has features that make it a direct link between the earlier lobe-finned fish and the later amphibians (figure ). With gills, scales, and fins, it was clearly a fish that lived its life in water. But it also has amphibian-like features. For one thing, its head is flattened like that of a salamander, with the eyes and nostrils on top rather than on the sides of the skull. This suggests that it lived in shallow water and could peer, and probably breathe, above the surface. The fins had become more robust, allowing the animal to flex itself upward to help survey its surroundings. And, like the early amphibians, Tiktaalik has a neck. Fish don’t have necks—their skull joins directly to their shoulders.
Most importantly, Tiktaalik has two novel traits that were to prove useful in helping its descendants invade the land. The first is a set of sturdy ribs that helped the animal pump air into its lungs and move oxygen from its gills (Tiktaalik could breathe both ways). And instead of the many tiny bones in the fins of lobe-finned fish, Tiktaalik had fewer and sturdier bones in the limbs—bones similar in number and position to those o every land creature that came later, including ourselves. In fact, its limbs are best described as part fin, part leg.