Evolution Diary

Fossil animals found in Arctic Canada provide a snapshot of fish evolving into land animals, scientists say.

University of Chicago fossil preparator, Tyler Keillor, discusses the iterative process of creating the model for Tiktaalik, the fossil discovery by paleontologist Neil Shubin that fills in the evolutionary gap between fish and land animals.

The finds are giving researchers a fascinating insight into this key stage in the evolution of life on Earth.

US palaeontologists have published details of the fossil “missing links” in the prestigious journal Nature.

The 383 million-year-old specimens are described as crocodile-like animals with fins instead of limbs that probably lived in shallow water.

Before these finds, palaeontologists knew that lobe-finned fishes evolved into land-living creatures during the Devonian Period.

But fossil records showed a gap between Panderichthys, a fish that lived about 385 million years ago which shows early signs of evolving land-friendly features, and Acanthostega, the earliest known tetrapod (four-limbed animals) dating from about 365 million years ago.

In 1999, palaeontologists Professor Neil Shubin, from the University of Chicago, and Professor Edward Daeschler, from the Academy of Natural Sciences in Philadelphia, set out to explore the Canadian Arctic in an attempt to find the “missing link” that would explain the transition from water to land.

After several years of searching with very little success, they hit the jackpot in 2004.

“The really remarkable find came when one of the crew found a snout of a flat-headed animal sticking out of the side of a cliff - that is totally what you want to find because if you are at all lucky the rest of the skeleton is back in the cliff,” said Professor Shubin.

The team found three near-complete, well-preserved fossils of the new species, Tiktaalik roseae, in an area of the Arctic called the Nunavut Territory. The largest measures almost 3m (9 ft) in length.

“When we got back into the lab we removed the rock from the bone, and we began to find some really significant stuff,” Professor Shubin told the BBC news website.
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