News / Science & Technology

Scientist: Ancient Fish Shows Signs of Rear-Leg Development

Reuters
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.
 
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 nine feet (2.7 meters).
 
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.

You May Like

Multimedia Obama Defends Immigration Action

Obama says with his executive action on immigration, enforcement resources will be focused on 'felons, not families; criminals, not children' More

US-Led Airstrikes in Syria Kill Over 900: Monitoring Group

British-based Syrian Observatory for Human Rights says the toll includes more than 50 civilians, five of them women and eight of them children More

Report: Obama Broadens US Combat Role in Afghanistan

The New York Times says resident Barack Obama has signed a classified order extending the role of US troops in Afghanistan for another year More

This forum has been closed.
Comments
     
There are no comments in this forum. Be first and add one

Featured Videos

Your JavaScript is turned off or you have an old version of Adobe's Flash Player. Get the latest Flash player.
New Skateboard Defies Gravityi
X
November 21, 2014 5:07 AM
A futuristic dream only a couple of decades ago, the hoverboard – a skateboard that floats above the ground - has finally been made possible. While still not ready for mass production, it promises to become a cool mode of transport... at least over some surfaces. VOA’s George Putic reports.
Video

Video New Skateboard Defies Gravity

A futuristic dream only a couple of decades ago, the hoverboard – a skateboard that floats above the ground - has finally been made possible. While still not ready for mass production, it promises to become a cool mode of transport... at least over some surfaces. VOA’s George Putic reports.
Video

Video Falling Gas Prices Impact US Oil Extraction

With the price of oil now less than $80 a barrel, motorists throughout the United States are benefiting from gas prices below $3 a gallon. But as VOA’s Kane Farabaugh reports, the decreasing price of petroleum has a downside for the hydraulic fracturing industry in the United States.
Video

Video Tensions Build on Korean Peninsula Amid Military Drills

It has been another tense week on the Korean peninsula as Pyongyang threatened to again test nuclear weapons while the U.S. and South Korean forces held joint military exercises in a show of force. VOA’s Brian Padden reports from the Kunsan Air Base in South Korea.
Video

Video Mama Sarah Obama Honored at UN Women’s Entrepreneurship Day

President Barack Obama's step-grandmother is in the United States to raise money to build a $12 million school and hospital center in Kogelo, Kenya, the birthplace of the president's father, Barack Obama, Sr. She was honored for her decades of work to aid poor Kenyans at a Women's Entrepreneurship Day at the United Nations.
Video

Video Gay Evangelicals Argue That Bible Does Not Condemn Homosexuality

More than 30 U.S. states now recognize same-sex marriages, and an increasing number of mainline American churches are blessing them. But evangelical church members- which account for around 30 percent of the U.S. adult population - believe the Bible unequivocally condemns homosexuality. VOA's Jerome Socolovsky reports that gay, lesbian, bisexual and transgender evangelicals are coming out. Backed by a prominent evangelical scholar, they argue that the traditional reading of the bible is wrong.
Video

Video Ebola Economic Toll Stirs W. Africa Food Security Concerns

The World Bank said Wednesday that it expects the economic impact of the Ebola outbreak on the sub-Saharan economy to cost somewhere betweenf $3 billion to $4 billion - well below a previously-outlined worst-case scenario of $32 billion. Some economists, however, paint a gloomier picture - warning that the disruption to regional markets and trading is considerable. Henry Ridgwell reports from London.
Video

Video Mexico Protests Escalate Over Disappearances

Protests in Mexico over 43 students missing since September continue to escalate, reflecting growing anger among Mexicans about a political system they view as corrupt, and increasingly tainted by the drug trade. Mounting outrage over the disappearances is now focused on the government of President Enrique Pena Nieto, accused of not doing enough to end insecurity in the country. More from VOA's Victoria Macchi.
Video

Video US Senate Votes Down Controversial Oil Pipeline - For Now

The U.S. Senate has rejected construction of a controversial pipeline to transport Canadian oil to American refineries. The $5 billion project still could be approved next year, but it faces a possible veto by President Barack Obama. As VOA’s Michael Bowman reports, the pipeline has exposed deep divisions in Congress about America’s energy future.
Video

Video Can Minsk Cease-fire Agreement Hold?

Growing tensions between government troops and separatists in eastern Ukraine further threaten a cease-fire agreement reached two months ago in the Belarusian capital of Minsk. Critics of U.S. policy in Ukraine say it is time the Obama administration gives up on that much-violated cease-fire and moves toward a new deal with Russia. VOA's Scott Stearns has more.
Video

Video Chaos, Abuse Defy Solution in Libya

The political and security crisis in Libya is deepening, with competing governments and, according to Amnesty International, widespread human rights violations committed with impunity. VOA’s Al Pessin reports from London.
Video

Video US Hosts Record 866,000 Foreign Students

Close to 900,000 international students are studying at American universities and colleges, more than ever before. About half of them come from Asia, mostly China. The United States hosts more foreign students than any other country in the world, and its foreign student population is steadily growing. Zlatica Hoke reports.
Video

Video Ferguson Church Grapples with Race Relations

Many white residents of Ferguson, Missouri, say they chose to live there because of the American Midwest community's diversity. So, they were shocked when a white police officer killed an unarmed black teenager in August – and shaken by the resulting protests and violence. Some local churches are leading conversations on how to go forward. VOA’s Ayesha Tanzeem reports.

All About America

AppleAndroid