World’s oldest tadpole discovered in Argentina — and it’s changing what we know about evolution

Call it a grand-phibian.

Scientists have unearthed a fossil of the world’s oldest tadpole in Argentina — a shock finding that could alter our understanding of amphibian evolution, experts say.

Paleontologists made the discovery of a juvenile of the ancient frog species notobatrachus degiustoi inadvertently — while searching for dinosaurs in the La Matilde Formation in Patagonia, Live Science reported.

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At 161 million years old, it’s the oldest pollywog on record by 20 million years, according to The Independent.

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“It’s not only the oldest tadpole known, but also the most exquisitely preserved,” said Mariana Chuliver, a biologist at Buenos Aires’ Maimonides University who helped author the research, published in the “Nature.”

Indeed, the specimen was in immaculate condition, complete with imprints of soft tissues, including the animal’s eyeballs, gills and nerves, which helped scientists make their identifications.

It was reportedly the first time an ancient tadpole had been matched to its adult counterpart on the fossil record.

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Impressively, the prehistoric pollywog was nearly as big as the grown-up version, measuring around 6 inches long with a 3-inch-long tail.

“Both [juvenile and adult] stages being giant is really hard to find in nature today,” said Chuliver.

By scientifically reuniting the adult and child, researchers were able to shed light on when frogs evolved to begin as tadpoles.

While researchers have stated that most frogs didn’t have a tadpole stage, this latest find proves that this was not the case, per Chuliver.

“It’s starting to help narrow the timeframe in which a frog becomes a frog,” said Ben Kligman, a paleontologist at the Smithsonian National Museum of Natural History who did not take part in the study.

In fact, tadpoles could’ve been around just as long as adult frogs have, thereby closing the book on this amphibian chicken-and-egg debate.

This primordial pond-skipper was shockingly similar to its modern-day descendant — down to the way they filter algae and other food from the water.