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.
You are a clone, then?
That's because new, better information has been discovered. Do you think there should be NO speculation on these issues until there is 100% certainty? The new, better information, and new, better speculation came from scientists doing science. That's the way science works. Nobody claims that science gets it 100% right the first time - it's a process of iteration, and moving closer to the truth. Can you think of a better approach to discovering natural truths?
LOL! Is that suppose to mean something to me? It does not and people can think what they like, that is what freedom is all about.
Funny #6, d.
The Eastern Newt (and its close relative the Striped Newt, N. perstriatus) are unique in that they undergo two metamorphoses. The first is the usual transformation from aquatic, gilled larva to an air-breathing terrestrial form. However in these two species there is a second, less striking metamorphosis to a breeding aquatic adult. The sexually immature land phase is usually called an Eft (left, top and middle, and below) while the aquatic adults are called Newts (bottom left). The Eastern Newt is divided into four subspecies. Adults reach lengths of nearly 5 inches, while Efts usually reach only about 3 inches. The Red-Spotted Newt gets its name from the many red spots that occur on its dorsal surface against the background color of brown to olive green in adults.
Oh please, you speak the typical scientific jargon that always leaves a way out when your theories are proven wrong.
a clone from mom and pop...
I can't imagine why they're so upset. It's just 19th century science. Fossils are so passe, and every time you find a missing link you have two new ones, one on each side. Let's face it. The numbers are against us.
No, I was beautifully and wonderfully made in God's image. I hope that doesn't cause you to melt or anything...:)
Was that agreement or disagreement of something I said.
Who says theory trumps mythology?
Welcome to FR.
Well, the bible-thumpers clearly favor mythology; that's been demonstrated over and over again.
Agreement. I thought you'd like to know you were in good company.
"a clone from mom and pop..."
Impossible. Sexually reproducing species don't produce clones. Unless you're not telling us something? :)
Do you refer to Christians as Bible-thumpers?
There isn't any evidence of humans being evolved from anything like this..
therefore your statement is based on whimsical ideas and theories. You live in a "what if" fantasy world.
Where is this conclusive evidence? Dr. Linkey couldn't even find the link!
I don't believe he did either , not smart enough.
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