Newly found species fills evolutionary gap between fish and land animals

EurekAlert (AAAS) ^ | 05 April 2006 | Staff

[PatrickHenry]

Paleontologists have discovered fossils of a species that provides the missing evolutionary link between fish and the first animals that walked out of water onto land about 375 million years ago. The newly found species, Tiktaalik roseae, has a skull, a neck, ribs and parts of the limbs that are similar to four-legged animals known as tetrapods, as well as fish-like features such as a primitive jaw, fins and scales.

These fossils, found on Ellesmere Island in Arctic Canada, are the most compelling examples yet of an animal that was at the cusp of the fish-tetrapod transition. The new find is described in two related research articles highlighted on the cover of the April 6, 2006, issue of Nature.

"Tiktaalik blurs the boundary between fish and land-living animal both in terms of its anatomy and its way of life," said Neil Shubin, professor and chairman of organismal biology at the University of Chicago and co-leader of the project.

Tiktaalik was a predator with sharp teeth, a crocodile-like head and a flattened body. The well-preserved skeletal material from several specimens, ranging from 4 to 9 feet long, enabled the researchers to study the mosaic pattern of evolutionary change in different parts of the skeleton as fish evolved into land animals.

The high quality of the fossils also allowed the team to examine the joint surfaces on many of the fin bones, concluding that the shoulder, elbow and wrist joints were capable of supporting the body-like limbed animals.

"Human comprehension of the history of life on Earth is taking a major leap forward," said H. Richard Lane, director of sedimentary geology and paleobiology at the National Science Foundation. "These exciting discoveries are providing fossil 'Rosetta Stones' for a deeper understanding of this evolutionary milestone--fish to land-roaming tetrapods."

One of the most important aspects of this discovery is the illumination of the fin-to-limb transition. In a second paper in the journal, the scientists describe in depth how the pectoral fin of the fish serves as the origin of the tetrapod limb.

Embedded in the fin of Tiktaalik are bones that compare to the upper arm, forearm and primitive parts of the hand of land-living animals.

"Most of the major joints of the fin are functional in this fish," Shubin said. "The shoulder, elbow and even parts of the wrist are already there and working in ways similar to the earliest land-living animals."

At the time that Tiktaalik lived, what is now the Canadian Arctic region was part of a landmass that straddled the equator. It had a subtropical climate, much like the Amazon basin today. The species lived in the small streams of this delta system. According to Shubin, the ecological setting in which these animals evolved provided an environment conducive to the transition to life on land.

"We knew that the rocks on Ellesmere Island offered a glimpse into the right time period and the right ancient environments to provide the potential for finding fossils documenting this important evolutionary transition," said Ted Daeschler of the Academy of Natural Sciences in Philadelphia, a co-leader of the project. "Finding the fossils within this remote, rugged terrain, however, required a lot of time and effort."

The nature of the deposits where the fossils were found and the skeletal structure of Tiktaalik suggests the animal lived in shallow water and perhaps even out of the water for short periods.

"The skeleton of Tiktaalik indicates that it could support its body under the force of gravity whether in very shallow water or on land," said Farish Jenkins, professor of organismic and evolutionary biology at Harvard University and co-author of the papers. "This represents a critical early phase in the evolution of all limbed animals, including humans--albeit a very ancient step."

The new fossils were collected during four summers of exploration in Canada's Nunavut Territory, 600 miles from the North Pole, by paleontologists from the Academy of Natural Sciences in Philadelphia, the University of Chicago and Harvard University. Although the team has amassed a diverse assemblage of fossil fish, Shubin said, the discovery of these transitional fossils in 2004 was a vindication of their persistence.

The scientists asked the Nunavut people to propose a formal scientific name for the new species. The Elders Council of Nunavut, the Inuit Qaujimajatuqangit, suggested "Tiktaalik" (tic-TAH-lick)--the word in the Inuktikuk language for "a large, shallow water fish."

The scientists worked through the Department of Culture, Language, Elders and Youth in Nunavut to collaborate with the local Inuit communities. All fossils are the property of the people of Nunavut and will be returned to Canada after they are studied.

###

The team depended on the maps of the Geological Survey of Canada. The researchers received permits from the Department of Culture, Language, Elders and Youth of the Government of Nunavut, and logistical support in the form of helicopters and bush planes from Polar Continental Shelf Project of Natural Resources Canada. The National Science Foundation and the National Geographic Society, along with an anonymous donor, also helped fund the project.

[ConsentofGoverned]

"*just a theory* is only making you look that much more the fool. What ISN'T *just a theory* in science?"
>>>>>>>>>>>>>>>>>>>............
Jump from the 50th story of the sears tower and tell us Gravity is just a theory..LOL

[Zavien Doombringer]

so, you do not agree that dad and mom's DNA didn't match up to create a smaller version of the two of them?

[yellowdoghunter]

Well we will just have to agree to disagree.

Maybe one day science will have some facts or maybe not. But I wouldn't hold my breath.

I must say though that people who believe in evolution are quick to assume a person who does not is illiterate when it comes to science. It does not help your argument.

[yellowdoghunter]

I see there is still no answer to the complexity of the cell or "molecular machinery"??????

Anyone???

Ya know, when you have to resort to 3rd grade attacks, you have lost the argument.

[MeanWestTexan]

When you watch movies do you wonder what happened in the space between the static frames, too?

You know, a movie is just a series of static pictures and your mind fills in the details between what happens in the gap of 1/6 of a second between each frame.

I suppose you see no evidence of motion.

[Condorman]

If this is even half as big a discovery as this makes it appear, why are nothing other than small fringe sites carrying it?

The story made the Yahoo! News science feed today at 11:00 am PST.

[Junior]

Not all Christians are "bible thumpers." The term originated with those who held the Good Book in one hand and "thumped" it with the fingers of the other when they were trying to stress a theological point. Nowadays it specifically refers to Biblical literalists -- which are actually only a small segment of the corpus of Christianity.

[blowfish]

Only the rabid 'bible-is-a-science-textbook' variety.

[CarolinaGuitarman]

"Jump from the 50th story of the sears tower and tell us Gravity is just a theory..LOL"

Gravity actually IS just a theory. It's actually called just that, the theory of gravity. Save your LOL for someone else. :)

[Ichneumon]

[And little do you know how enormous is the cross-validating evidence and repeatedly validated conclusions of evolutionary biology.]

Great, here's your chance back up that statement.

Okay.

[Huge predators would have lurked in Tiktaalik's rivers and lakes,]

Oh really?! Where is the ENORMOUS, CROSS-VALIDATED EVIDENSE for this drivel?

Gosh, you mean aside from the vast numbers of large predators fossils found in the Devonian, bite marks found on numerous fossil fish matching the jaws of the fossil predators, fossil predators found with the fossilized remains of their prey in their stomachs, and so on and so on and so on? Oh, but that doesn't count, because you were grossly ignorant of it, right?

This guy was 20 feet long, with a skull four feet wide and bony armor two inches thick -- is that "huge" enough for you?

["Land had no predators,"]

Really? Where is the ENORMOUS, CROSS-VALIDATED EVIDENSE for this drivel?

You mean besides the vast amount of Devonian (and pre-Devonian) land strata which has been examined, all found to be lacking any animals whatsoever larger than a millipede?

Now, it's *your* turn. Provide any actual evidence whatsoever justifying your spittle-flinging rant that these statements are "drivel". We'll wait.

[Zavien Doombringer]

And what Myth is in the Bible?

[CarolinaGuitarman]

"so, you do not agree that dad and mom's DNA didn't match up to create a smaller version of the two of them?"

No, I don't agree. It doesn't happen. Sexually reproducing species do not produce clones. Biology 101.

[Zavien Doombringer]

That's one big snapping turtle!

[mlc9852]

Well, I think you use the term pejoratively and there are quite a few Christians in the US. There are even some here on FR. But if it makes you feel superior to insult those who believe the Bible, go for it.

[Zavien Doombringer]

so, mixing of DNA doesn't produce clones? Same concept, just a different blender

[Junior]

It's Just a Theory
(with apologies to Blue Oyster Cult)
by Junior

Darwin's time has come
Evolution now is gone
Creos don't like the theory
We're certain it's just plain wrong.
They can be like we are

Come on creos ... It's just a theory
No need to listen ... It's just a theory
Darwin's on the outs ... It's just a theory
All his links are missin'...

S. J. Gould is done
P.E. now is gone
Behe, Miller, Hovind
Will now tell us how it's done
Behe, Miller, Hovind...

Americans believe the creos ... Behe, Miller, Hovind
Americans believe the creos ... Tell us how it's done
And more are joining us everyday ... You can be like we are

Come on creos ... It's just a theory
No need to listen ... It's just a theory
Darwin's on the outs ... It's just a theory
All his links are missin'...

Evolutionary biology
Was here but now it's gone
We'll replace it with ID
Regardless if it's really wrong
We regard it as a kind of tool
It's just a wedge to get God in school
To see how many we can fool
Saying, "join the creos..."

Come on creos ... And then they came
Flocked in droves ... We ain't no slime
Turned the clock backward in time
You'll become like we are
No need for research
You'll become like we are

Come on creos ... It's just a theory

[PatrickHenry]

The story made the Yahoo! News science feed today at 11:00 am PST.

Wow! My only sources were Nature and the online news service of The American Association for the Advancement of Science. I guess now it's official.

[Sofa King]

Holy crap, that thing's awesome!

[ConsentofGoverned]

illusion of motion yes, but from my side it supports what I said in a very succinct way..the mind is fooled and we suspend credulity to accept the movie as real or a real possibility..guess thats why I do not watch many movies aside from Hollywood's inability to write a decent script.

[CarolinaGuitarman]

" Maybe one day science will have some facts or maybe not."

There already are facts in science.

"I must say though that people who believe in evolution are quick to assume a person who does not is illiterate when it comes to science. It does not help your argument."

When someone demonstrates they do not know the first principles of science, it is a reasonable inference that they are scientifically illiterate.