Scientists have discovered the oldest known fossil of a giant tadpole that roamed more than 160m years ago.
The new fossil, found in Argentinasurpassing the previous old record holder by about 20m years.
Imprinted in a slab of sandstone are parts of the tadpole’s skull and spine, along with impressions of its eyes and nerves.
“It is not only the oldest tadpole known, but also the most exquisitely preserved,” said study author Mariana Chuliver, a biologist at Buenos Aires’ Maimonides University.
Researchers know that frogs have been jumping around as far back as 217m years ago. But exactly how and when they evolved to begin as tadpoles remains unclear.
This new discovery adds some clarity to that timeline. At about 6 inches (16 cm) long, the tadpole is a younger version of an extinct giant frog.
“It starts to help narrow down the time frame in which a frog becomes a frog,” said Ben Kligman, a paleontologist at the Smithsonian National Museum of Natural History who was not involved in the research.
The results were published in the journal Nature on Wednesday.
The fossil is strikingly similar to today’s tadpoles – even containing remains of a gill system that modern-day tadpoles use to sift food particles from water.
That means the amphibians’ survival strategy has been tried and true for millions of years, helping them survive several mass extinctions, Kligman said.
