Walking 'fish' fossil is missing link

A newly discovered fossil 'fish' is believed to be a missing link in the puzzle as to how fish evolved into land-dwelling animals.

The new species, which has been named Tiktaalik roseae, looks like a crocodile but has lobe-fins like those of ancient fishes, as well as gills for breathing under water.

The animal also has some features common in land animals, such as a neck, "elbows" and "wrists" on its fin-like limbs which would have enabled it to move around on land.

The new tetrapod-like fossil was discovered in Canada and was described this week in the journal Nature by Edward Daeschler of Philadelphia's Academy of Natural Sciences, Neil Shubin of the University of Chicago, Farish Jenkins of Harvard University in Cambridge, Massachusetts and a number of other colleagues.

Dr Andrew Milner, a paleontologist at The Natural History Museum in London said on the NHM website that the discovery was a major find.

"This is the fossil of the year and a most significant addition to our knowledge. It is a stepping-stone in the water-land transition showing us a permutation of features not seen before, notably the combination of lobe-fins with the beginnings of a neck."

Tiktaalik roseae is believed to have lived about 375 million years ago in the late Devonian period, and is thought to have grown to sizes of around 2.74m/9 feet.

What's so unique about this discovery, says Milner, is that the scientists in Canada discovered three very large specimens which have articulated limbs so scientists are now able to study them to determine how they were constructed and where they sit in the phylogeny alongside related organisms.

For more details on the discovery see the paper: Daeschler EB, Shubin NH and Farish AJ (2006) - A Devonian tetrapod-like fish and the evolution of the tetrapod body plan. Nature 440, 757-763 (6 April 2006).