Arctic Fossils mark move to land

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Arctic fossils mark move to land

By Rebecca Morelle

BBC News science reporter

 

 

 

The fossil is remarkably well preserved (Image: Ted Daeschler)

 

 

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Fossil animals found in Arctic Canada provide a snapshot of fish evolving

into land animals, scientists say.

 

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.

 

'Missing link'

 

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 land-living 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.

 

Crocodile-like

 

The creature shares some characteristics with a fish; it has fins with

webbing, and scales on its back.

 

But it also has many features in common with land animals. It has a flat

crocodile-like head with eyes positioned on top and the beginnings of a

neck - something not seen in fish.

 

" When we look inside the fin, we see a shoulder, we see an elbow, and we see

an early version of a wrist, which is very similar to that of all animals

that also walk on land, " said Professor Shubin.

 

 

The scientists think the creature lived in the shallows

 

" Essentially we have an animal that is built to support itself on the

ground. "

 

The scientists believe the position of the creature's eyes suggest it

probably lived in shallow water.

 

" We are capturing a very significant transition at a key moment of time.

What is significant about the animal is that it is a fossil that blurs the

distinction between two forms of life - between an animal that lives in

water and an animal that lives on land. "

 

Dr Andrew Milner, a palaeontologist from the Natural History Museum, UK,

said it is unusual to find a fossil like this in such good condition.

 

" This material is amazing because it includes a nearly complete skeleton -

which is always handy because instead of assembling the fossil from bits we

can see the whole skeleton and be sure that this is how the animal was put

together. "

 

Professor Jennifer Clack, from the University of Cambridge, said that the

find could prove to be as much of an " evolutionary icon " as Archaeopteryx -

an animal believed to mark the transition from reptiles to birds.

 

" The discovery of the Tiktaalik gives hope of equally ground-breaking finds

to come, " she said.

 

A cast of one of the fossils will be on display at the Science Museum in

London from Thursday.