Frogs and salamanders and a common ancestor, oh my!

Researchers find missing evolutionary link between frogs and salamanders

Researchers from the University of Calgary, the University of Toronto and McGill University have solved one of the greatest mysteries in vertebrate evolution.

Dr. Jason Anderson of the University of Calgary Faculty of Veterinary Medicine, Dr. Robert Reisz of the University of Toronto and Nadia Fröbisch, a PhD candidate at McGill University's Redpath Museum and colleagues, have proven conclusively that all modern frogs, toads and salamanders descend from a common amphibian ancestor that existed over 200 million years ago. Their results were published May 21 in the journal Nature.

Their findings derive from exhaustive research conducted on Gerobatrachus hottoni (or "Hotton's elder frog,") an ancient fossil discovered in Texas in 1995 by the late Smithsonian Institution researcher Nicholas Hotton. According to the University of Calgary, the fossil went unstudied until it was later "rediscovered" by Dr. Anderson's team.

Gerobachtrachus exhibits a mixture of salamander and frog features in its skull, backbone and teeth.

Moreover, Fröbisch discovered that it had two fused bones in its ankle. "This is a feature usually uniquely seen in salamanders and no other group," she explained.

"The question of whether frogs, toads and salamanders had a common ancestor has been plaguing science for a very long time," Fröbisch said. "There have actually been papers on this topic for 120 years or more."

"The dispute arose because of a lack of transitional forms. This fossil seals the gap," said Anderson, lead author of the study.

"It's very exciting to be doing this kind of breakthrough research," added Fröbisch. "It's actually kind of surreal."