Missing link

Scientists have found a "missing link" between fish and land animals that include the prehistoric ancestors of humans. The discovery of the new animal, called Tiktaalik (meaning a large freshwater fish), was reported in Nature (Vol 440, No 7085, April 6, 2006).

Found in Ellesmere Island in northern Canada, the fossil shows how fins on freshwater species began transforming into limbs some 370 million years ago. "This animal represents the transition from water to land -- the part of history that includes ourselves," said Neil Shubin, palaeontologist at the University of Chicago, USA, and co-leader of a team that uncovered three nearly complete fossils measuring up to three metres in 2004.

Tiktaalik had a crocodile-like head and strong, bony fins. It had a mobile neck and had lost the bony coverings of the gills that fish use to fan water to maximise their oxygen intake. This suggests that the fish may have been able to breathe in air. Strong and bony fins probably extended like legs to help it move through shallow, subtropical waters or even on land, say researchers. They found a wrist-like arrangement near the tip of the fin, so that the end could bend forward and provide foot-like support. Unlike other fish, the new species had strong ribs. "So this animal must have developed these structures for life in the shallows and making excursions on to land," researchers say.

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