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A missing link settles debate over the origin of frogs and salamanders
May 22, 2008The description of an ancient amphibian that millions of years ago swam in quiet pools and caught mayflies on the surrounding land in Texas has set to rest one of the greatest current controversies in vertebrate evolution. The discovery was made by a research team led by scientists at the University of Calgary.
The examination and detailed description of the fossil, Gerobatrachus hottoni (meaning Hotton's elder frog), proves the previously disputed fact that some modern amphibians, frogs and salamanders evolved from one ancient amphibian group called temnospondyls.
The discovery is described for the first time in the prestigious international research journal Nature.
"The dispute arose because of a lack of transitional forms. This fossil seals the gap," says Jason Anderson, assistant professor, University of Calgary Faculty of Veterinary Medicine and lead scientist in the study.
The Gerobatrachus fossil provides a much fuller understanding of the origin and evolution of modern 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 tympanic ear (ear drum). It also has a lightly built and wide skull similar to that of a frog. 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 Robert Reisz, professor, University of Toronto Mississauga and second author on the paper.
Gerobatrachus was originally discovered 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 Anderson's team. It took countless hours of work on the small, extremely delicate fossil 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 Anderson. "Hopefully we won't ever learn about their extinction."
University of Calgary
"The dispute arose because of a lack of transitional forms. This fossil seals the gap," says Jason Anderson, assistant professor, University of Calgary Faculty of Veterinary Medicine and lead scientist in the study.
The Gerobatrachus fossil provides a much fuller understanding of the origin and evolution of modern 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 tympanic ear (ear drum). It also has a lightly built and wide skull similar to that of a frog. 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 Robert Reisz, professor, University of Toronto Mississauga and second author on the paper.
Gerobatrachus was originally discovered 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 Anderson's team. It took countless hours of work on the small, extremely delicate fossil 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 Anderson. "Hopefully we won't ever learn about their extinction."
University of Calgary
Amphibian News and Current Amphibian Events RSSDying frogs sign of a biodiversity crisis
Devastating declines of amphibian species around the world are a sign of a biodiversity disaster larger than just frogs, salamanders and their ilk, according to researchers from the University of California, Berkeley.
New study points to agriculture in frog sexual abnormalities
A farm irrigation canal would seem a healthier place for toads than a ditch by a supermarket parking lot.
New findings on immune system in amphibians
Krakow/Halle. Major Histocompatibility Complex (MHC) genes produce proteins that are crucial in fighting pathogen assault. Researchers from the Jagiellonian University in Krakow and from the Helmholtz Centre for Environmental Research (UFZ) characterized genetic variation and detected more than one MHC class II locus in a tailed amphibian.
New study reveals large scale conservation essential
Scientists were surprised with findings of a recent study that reveals many animal species believed to persist in small contained areas actually need broad, landscape level conservation to survive.
Probiotic bacteria protect endangered frogs from lethal skin disease
Laboratory tests and field studies conducted by James Madison University (JMU) researchers continue to show promise that probiotic bacteria can be used to help amphibian populations, including the endangered yellow-legged frog, fend off lethal skin diseases.
Priority regions for threatened frog and toad conservation in Latin America
Nearly 35% of all amphibians are now threatened of extinction raising them to the position of the most endangered group of animals in the world.
Opening a channel for salt retention
A research team has developed the first small molecule that can reversibly activate a key protein involved in balancing sodium levels, paving the way for drugs that can treat low blood pressure and related conditions.
Road losses add up, taxing amphibians and other animals
When frogs hit the road, many croak. Researchers found more than 65 animal species killed along a short stretch of roads in a Midwestern county. Nearly 95 percent of the total dead were frogs and other amphibians, suggesting that road-related death, or road-kill, possibly contributes to their worldwide decline, a trend that has concerned and puzzled scientists for decades.
Early exposure to common weed killer impairs amphibian development
Tadpoles develop deformed hearts and impaired kidneys and digestive systems when exposed to the widely used herbicide atrazine in their early stages of life, according to research by Tufts University biologists.
Found: First lungless frog
Researchers have confirmed the first case of complete lunglessness in a frog, according to a report in the April 8th issue of Current Biology, a publication of Cell Press. The aquatic frog Barbourula kalimantanensis apparently gets all the oxygen it needs through its skin.
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