Researchers examine Tiktaalik fossil

Researchers in Philadelphia are picking through the fossil bones of an aquatic animal named tiktaalik to see how our evolutionary ancestors emerged onto land from the water.

Researchers in Philadelphia are picking through the fossil bones of an aquatic animal named Tiktaalik [tick-tah-lick] to see how our evolutionary ancestors emerged onto land from the water.

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Reconstructions of Tiktaalik show the animal as a finned fish-like creature with a crocodilian-looking head.

Its discovery in the Canadian arctic several years ago was an exciting find for paleontologists, says Jason Downs at the Academy of Natural Sciences.

Downs: Tiktaalik roseae has the distinction of being the finned vertebrate more closely related to limbed vertebrates than any other known.

In other words, Tiktaalik is part of the evolutionary transition from water to land.

It has fins and gills, but other structures that resemble limbed land animals.

In a report released today in the journal Nature, downs and his colleagues describe the bones inside the skull – such as the gills and the roof of the mouth.

Downs: There are certain aspects of the gill skeleton that it shares with limbed forms, certain aspects to the gill skeleton that we don’t see in primitive finned forms.

One bone in particular demonstrates a shift from its use in gill breathing, to its eventual function as a hearing bone in more evolved animals.

Downs says scientists are still debating aspects of Tiktaalik, such as how much air it breathed, versus breathing under water.