wes_von_papineäu
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CANWEST NEWS SERVICE (Toronto, Ontario) 21 May 08 Fossil 'seals gap' in frog debate
An ancient amphibian that landed in a Calgary lab has settled a long-running debate over the evolution of frogs and amphibians.
The fossilized creature, known as Gerobatrachus hottoni, proves that some modern amphibians, frogs and salamanders evolved from an ancient amphibian group called temnospondyls, a Canadian-led team reports in the journal Nature.
"This fossil seals the gap," says team leader Jason Anderson, of University of Calgary Faculty of Veterinary Medicine.
A field party from the Smithsonian Institution found the fossil in Texas in 1995.
Gerobatrachus boasts both frog and salamander features - it has two fused bones in the ankle normally only seen in salamanders, as well as a lightly built and wide skull similar to that of a frog, the researchers report.
The tiny fossil, measuring 11 centimetres long, also points to when salamanders and frogs evolved into two distinct groups.
"With this new data, our best estimate indicates that frogs and salamanders separated from each other sometime between 240 and 275 million years ago, much more recently than previous molecular data had suggested," co-author Robert Reisz, professor, University of Toronto Mississauga says in a statement released with the study.
A field party from the Smithsonian Institution found the fossil in Texas in 1995. But it remained unstudied until it was "rediscovered" by Anderson's team, which removed the overlying layers of rock to reveal the ancient skeleton inside.
http://www.canada.com/topics/news/national/story.html?id=fc89bd04-aa41-4e6c-a372-cbe71fce1eab
Photo at URL below
THE TELEGRAPH (London, UK) 21 May 08 Missing link fossil settles frog evolution debate (Roger Highfield)
Gerobatrachus hottoni, the long sought missing link that settles a debate over the origin of frogs and salamanders.
The origin of today’s amphibians is controversial because of a lack of intermediate forms to show which ancient creatures evolved into frogs and salamanders.
Now a Texan fossil, Gerobatrachus hottoni ("Hotton’s elder frog") from around 300 million years ago, proves the previously disputed fact that some modern amphibians, frogs and salamanders evolved from one group of ancient primitive amphibians called temnospondyls, some of which were up to 1.5 metres long.
The description of the ancient 4.5 inch amphibian that millions of years ago swam in quiet pools and caught mayflies in Texas has set to rest one of the greatest current controversies in vertebrate evolution, say scientists at the University of Calgary, who report the find in the journal Nature.
"The dispute arose because of a lack of transitional forms. This fossil seals the gap," says Dr Jason Anderson, lead scientist.
The Gerobatrachus fossil has the chassis of an archaic temnospondyl, along with many characteristic features seen in modern frogs, toads and salamanders.
The fossil suggests that modern amphibians may have come from two groups, with frogs, toads and salamanders related to temnospondyls, while another type of modern amphibian - the earthworm-like caecilians - is more closely related to the lepospondyls, another group of archaic amphibians.
The skull, backbone and teeth of Gerobatrachus have a mixture of frog and salamander features - the fossil has two fused bones in the ankle, which is normally only seen in salamanders, and a very large ear drum.
It also has a lightly built and wide skull similar to that of a frog, while its backbone is exactly intermediate in number between the modern frogs and salamanders and more primitive amphibians.
The new fossil also addresses a controversy over molecular clock estimates, or the general time salamanders and frogs evolved into two distinct groups.
"With this new data our best estimate indicates that frogs and salamanders separated from each other sometime between 240 and 275 million years ago, much more recently than previous molecular data had suggested," says Prof Robert Reisz, University of Toronto Mississauga and second author .
Gerobatrachus was originally discovered in "Don’s Dump Fish Quarry", in Texas in 1995 by a field party from the Smithsonian Institution that included the late Nicholas Hotton, for whom the fossil is named.
It remained unstudied until it was "rediscovered" by Dr Anderson’s team. Countless hours of work on the small, extremely delicate fossil were needed to remove the overlying layers of rock and uncover the bones to reveal the anatomy of the spectacular looking skeleton.
"It is bittersweet to learn about frog origins in this Year of the Frog, dedicated to informing the public about the current global amphibian decline," continues Dr Anderson. "Hopefully we won’t ever learn about their extinction."
http://www.telegraph.co.uk/earth/main.jhtml?view=DETAILS&grid=&xml=/earth/2008/05/21/scifrog121.xml
An ancient amphibian that landed in a Calgary lab has settled a long-running debate over the evolution of frogs and amphibians.
The fossilized creature, known as Gerobatrachus hottoni, proves that some modern amphibians, frogs and salamanders evolved from an ancient amphibian group called temnospondyls, a Canadian-led team reports in the journal Nature.
"This fossil seals the gap," says team leader Jason Anderson, of University of Calgary Faculty of Veterinary Medicine.
A field party from the Smithsonian Institution found the fossil in Texas in 1995.
Gerobatrachus boasts both frog and salamander features - it has two fused bones in the ankle normally only seen in salamanders, as well as a lightly built and wide skull similar to that of a frog, the researchers report.
The tiny fossil, measuring 11 centimetres long, also points to when salamanders and frogs evolved into two distinct groups.
"With this new data, our best estimate indicates that frogs and salamanders separated from each other sometime between 240 and 275 million years ago, much more recently than previous molecular data had suggested," co-author Robert Reisz, professor, University of Toronto Mississauga says in a statement released with the study.
A field party from the Smithsonian Institution found the fossil in Texas in 1995. But it remained unstudied until it was "rediscovered" by Anderson's team, which removed the overlying layers of rock to reveal the ancient skeleton inside.
http://www.canada.com/topics/news/national/story.html?id=fc89bd04-aa41-4e6c-a372-cbe71fce1eab
Photo at URL below
THE TELEGRAPH (London, UK) 21 May 08 Missing link fossil settles frog evolution debate (Roger Highfield)
Gerobatrachus hottoni, the long sought missing link that settles a debate over the origin of frogs and salamanders.
The origin of today’s amphibians is controversial because of a lack of intermediate forms to show which ancient creatures evolved into frogs and salamanders.
Now a Texan fossil, Gerobatrachus hottoni ("Hotton’s elder frog") from around 300 million years ago, proves the previously disputed fact that some modern amphibians, frogs and salamanders evolved from one group of ancient primitive amphibians called temnospondyls, some of which were up to 1.5 metres long.
The description of the ancient 4.5 inch amphibian that millions of years ago swam in quiet pools and caught mayflies in Texas has set to rest one of the greatest current controversies in vertebrate evolution, say scientists at the University of Calgary, who report the find in the journal Nature.
"The dispute arose because of a lack of transitional forms. This fossil seals the gap," says Dr Jason Anderson, lead scientist.
The Gerobatrachus fossil has the chassis of an archaic temnospondyl, along with many characteristic features seen in modern frogs, toads and salamanders.
The fossil suggests that modern amphibians may have come from two groups, with frogs, toads and salamanders related to temnospondyls, while another type of modern amphibian - the earthworm-like caecilians - is more closely related to the lepospondyls, another group of archaic amphibians.
The skull, backbone and teeth of Gerobatrachus have a mixture of frog and salamander features - the fossil has two fused bones in the ankle, which is normally only seen in salamanders, and a very large ear drum.
It also has a lightly built and wide skull similar to that of a frog, while its backbone is exactly intermediate in number between the modern frogs and salamanders and more primitive amphibians.
The new fossil also addresses a controversy over molecular clock estimates, or the general time salamanders and frogs evolved into two distinct groups.
"With this new data our best estimate indicates that frogs and salamanders separated from each other sometime between 240 and 275 million years ago, much more recently than previous molecular data had suggested," says Prof Robert Reisz, University of Toronto Mississauga and second author .
Gerobatrachus was originally discovered in "Don’s Dump Fish Quarry", in Texas in 1995 by a field party from the Smithsonian Institution that included the late Nicholas Hotton, for whom the fossil is named.
It remained unstudied until it was "rediscovered" by Dr Anderson’s team. Countless hours of work on the small, extremely delicate fossil were needed to remove the overlying layers of rock and uncover the bones to reveal the anatomy of the spectacular looking skeleton.
"It is bittersweet to learn about frog origins in this Year of the Frog, dedicated to informing the public about the current global amphibian decline," continues Dr Anderson. "Hopefully we won’t ever learn about their extinction."
http://www.telegraph.co.uk/earth/main.jhtml?view=DETAILS&grid=&xml=/earth/2008/05/21/scifrog121.xml