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Ancient Fish Fossil Shows Signs of Rear-Leg Development


Science & Tech  (tags: archaeology, paleontology, fossils, fish, evolution, science, research, scientists, discovery, history, study )

Michael
- 337 days ago - cbc.ca
Fossils of an ancient fish species discovered in the Canadian Arctic show that hind legs evolved from fins some 375 million years ago, challenging a theory that they developed only after vertebrates took to land, according to research published this week.



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Comments

Michael O. (175)
Tuesday January 14, 2014, 7:45 pm
The remains of the fish, the Tiktaalik roseae, were discovered in 2004 on southern Ellesmere Island in northern Canada by a team of scientists that included a now-deceased Harvard University professor, Farish Jenkins, according to the findings published in the Proceedings of the National Academy of Sciences, a scientific journal.

Researchers had initially focused only on specimens containing the front portion of the fish but subsequently discovered pelvises and partial pelvic fin material from the rear portion that were comparable to those of some early four-legged animals, with a ball-and-socket hip joint.

"This is an amazing pelvis, particularly the hip socket, which is very different from anything that we knew of in the lineage leading up to limbed vertebrates," Ted Daeschler, associate curator of vertebrate zoology at Drexel University in Philadelphia and a co-author of the study, said in a statement.

The prevailing scientific understanding, Daeschler said, was based on "a 'front-wheel drive' idea that these animals were primarily using their front limbs for locomotion," while hind limbs were small and not necessarily used for movement.

"It looks like this shift actually began to happen in fish, not in limbed animals," Neil Shubin, a University of Chicago professor and co-author of the study, said in the statement. "It's reasonable to suppose with those big fin rays that Tiktaalik used its hind fins to swim like a paddle. But it's possible it could walk with them as well."

The Tiktaalik roseae looked like a cross between a fish and a crocodile, with lobe fins, a broad flat head and sharp teeth, according to Drexel. It hunted in shallow freshwater environments and grew to a length of up to 2.7 metres.

It had gills, scales and fins, but also features associated with four-legged animals a mobile neck, a robust ribcage and primitive lungs the university said. Its large forefins had shoulders, elbows and partial wrists, allowing it to support itself on ground.

Such features make the fish one of the best-known transitional species between fish and land-dwelling tetrapods, or animals with two pairs of limbs, the university said.
 

Natasha Salgado (576)
Wednesday January 15, 2014, 8:20 am
Good thing these weren't Canadian Scientists otherwise they'd be de-funded by the Conservatives...just remembering the science books disgrace. Thx Michael
 

Past Member (0)
Thursday January 16, 2014, 4:44 am
Thanks, interesting. But I really hate have to relearn what I once was told was true.
 

Fi T. (16)
Thursday January 16, 2014, 4:47 am
Preserve every life for the evidence of development
 

Azle B. (17)
Thursday January 16, 2014, 8:38 am
Links in the evolutionary chain are alwaysimportant to the development of science and understanding of sspecies.
 

Roger Garin-michaud (113)
Thursday January 16, 2014, 12:02 pm
noted, thanks
 

Birgit W. (152)
Thursday January 16, 2014, 1:38 pm
Interesting, thanks Michael.
 

Debra G. (0)
Thursday January 16, 2014, 1:40 pm
We now have the direct link showing Republicans/creationists "walked" together with dinosaurs: both are swamp-dwelling, sharp-toothed, belly-crawling, flat-headed crocodilians.
 

Robert O. (12)
Friday January 17, 2014, 12:30 am
Thanks Michael.
 

Kerrie G. (135)
Friday January 17, 2014, 3:39 am
Noted, thanks.
 

Melania Padilla (185)
Saturday January 25, 2014, 4:38 pm
Another thing to add to long, long history of evolution :)
 
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