Posted on 04/05/2006 10:32:31 AM PDT by 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.
Interesting read, but what would REALLY spark my interest, and what the article fails to mention, is how they breathed. Gills? Lungs? Somewhere in between? What?
Ah well.
BTW, nice tag line.
Great. All they've done is create two new gaps on either side of the previous one...
It is a scientific theory. There is a significance difference that you should understand.
Actually shes the link between Buckwheat and Weezie on the Jeffersons..
Thanks for the article!
So, did it taste like chicken, or fish?
That means genetic information can be acquired by critters independent of the "tree of life" formulation.
That doesn't make Creationism correct (obviously), but it does suggest that doctrinaire adherence to a rigid, self-contained "tree of life" mantra really isn't theologically diferent from the Creationist point of view.
Gad!
According to the numbers provided here the land mass once located almost 6,000 miles away 375 million years ago had to move at a rate of 2.2 inches per year toward the north pole; is that correct?
That means genetic information can be acquired by critters independent of the "tree of life" formulation.
by viruses for example
Or, by, for example, recombinant DNA technology.
If this is even half as big a discovery as this makes it appear, why are nothing other than small fringe sites carrying it?
"Fin"nish?
Doesn't that describe a critter that has fins but can walk with jointed bones on land?
Gravity is law I think.
I wanted to add earlier, but didn't, that this is another case of SLOPPY WRITING. If the spot was on the Equator, then it was TROPICAL, not SUBTROPICAL. And, no, Brazil does not have a SUBTROPICAL climate.
Makes you feel better, doesnt it?
Wrong: A scientific theory is of a higher order than proof or a fact. Evolution is a observed fact, the explanation of the observed fact (evolution) is the Theory of Evolution.
All these fish are alive today, thus I'm wondering what the significance of this find is.
Well, I suspect the total motion is less than 6,000 miles as Ellesmere Island isn't RIGHT at the north pole today, and it didn't have to be RIGHT at the equator...just near it...375 million years ago. so maybe actually 5,000 miles.
But 2.2 inches a year is a typical plate motion speed; North America is moving about that fast right now. The fastest plate in the world is moving over 9 inches a year.
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