Tiktaalik is a 375 million year old fossil discovered in Arctic Canada by a team of researchers led by Neil Shubin, Edward Daeschler, and Farish Jenkins in the year 2006. Tiktaalik is technically a fish with scales and gills, however has the flattened head of a crocodile and unusual fins.
Due to presence of a skull, neck, ribs, and parts of a fin that resemble the earliest limbed animals, in addition to fins and scales like a fish, Tiktaalik becomes a representative of the transition between non-tetrapod vertebrates (“fish”) and early tetrapods such as Acanthostega and Ichthyostega, known from fossils about 365 million years old.
Fossils or organisms that show the intermediate states between an ancestral form and that of its descendants are referred to as transitional forms.
Paleontologists have known that land animals first appeared in the Devonian Period but a connecting link between sea and land animals was always missing. But with the discovery of Tiktaalik allows us to reach this evolutionary milestone by bridging the gap between fish and land roaming organisms.
Team of Neil shubin collected the fossils during four summer explorations on Ellesmere Island in Canada’s Nunavut Territory. They turned to the people of Nunavut, who retain ownership of the fossils, for help in naming the new creature. The Nunavut Elders Council suggested the name “Tiktaalik” (tic-TA-lick), their word for a large, shallow-water fish.
As described above Tiktaalik had the strong wrist bones, neck, shoulders, and thick ribs of a four-legged vertebrate, which allowed it to adapt to dry land lifestyle for vertebrates, 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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Image Credit : Tiktaalik @ OpenStax