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Biologists say they have unraveled the DNA of thecoelacanth, a "living fossil" fish whose ancient lineage offer new information on how life in the sea crept onto land hundreds of millions of years ago.

The prehistoric-looking blue creature was pulled out of the water in 1938 by a South African fisherman. It's a 1.5-metre-long coelacanth, a type of fish that had been thought to have become extinct 70 million years earlier. It can grow up to two meters (6.5 feet) in length and weigh as much as 91 kilos (200 pounds). Coelacanths have four large, fleshy fins, which some scientists believe could have been the predecessors of limbs.

The study, published in the journal Nature, suggested that another fish called the lungfish, which also has four limbs, had more genes in common with land-based animals.

Even so, the coelacanth is a remarkable source, for it will help show which genes were squeezed out, and which emerged, in the touted sea-to-land transition.

Professor Kerstin Lindblad-Toh, from the University of Uppsala in Sweden and the Broad Institute of MIT and Harvard in the US, said:

"What we can see is that while the genome as whole changes, the protein-coding genes - that make the living fish - are much more stable and much more unchanging," said Professor Kerstin Lindblad-Toh, from the University of Uppsala in Sweden and the Broad Institute of MIT and Harvard.

"And if you think about it, this might be correlated to the fact that the coelacanth lives in a rather extreme and stable environment.

"It lives several hundred meters down in the ocean, and it may also be in an environment where it doesn't have a lot of competitors. So maybe it adapted to that environment a long time ago and it doesn't have a huge need for change."