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Oldest known tadpole fossil dates back 161 million years

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Paleontologists have discovered the well-preserved fossilized remains of an early anuran tadpole. Notobatrachus degiustoi At Estancia La Matilde in Patagonia, Argentina.

Reproducing the lives of tadpoles and adults Notobatrachus degiustoi. Image credit: Gabriel Rio.

Frogs and toads belong to a group of tailless amphibians called anurans.

They are characterized by a biphasic life cycle, with an aquatic larval (tadpole) stage followed by an adult (frog) stage.

Adult anurans remain in the fossil record until the late Triassic period (approximately 217 to 213 million years ago), but tadpoles have not been recorded before the Cretaceous period (approximately 145 million years ago). Not yet.

“Tadpoles are free-living, non-reproductive anuran aquatic larvae that undergo morphological and ecological changes over a short period of time before reaching the adult reproductive stage. “We need to go through a metamorphosis stage that involves profound changes in our lives.” And her colleagues.

“This rapid metamorphosis in anurans is the most extreme among extant tetrapods, with tadpoles representing a highly derived larval stage.”

The authors examined well-preserved tadpole fossils. Notobatrachus degiustoi from Formation of La Matilde In Patagonia.

This giant anuran lived during the Middle Jurassic Period, 168 to 161 million years ago.

This species is also represented by a large number of excellently preserved adult specimens from the same locality.

Notobatrachus degiustoi Tadpole. Image credit: Chubar others., doi: 10.1038/s41586-024-08055-y.

According to the team, the tadpoles Notobatrachus degiustoi It was almost 16 centimeters (6.3 inches) long.

The head, most of the body, and part of the tail were visible, as were the eyes, nerves, and forelimbs, suggesting that the tadpole was in a later stage of metamorphosis.

Together, they show that key traits of today’s tadpoles, such as filter-feeding systems, had already evolved in early anurans about 161 million years ago.

“The exquisite preservation of the tadpole, including its soft tissues, shows features related to the filter-feeding mechanism characteristic of living tadpoles,” the researchers said.

“What is noteworthy is that both Notobatrachus degiustoi Tadpoles and adults reached large sizes, proving that tadpole gigantism occurred among stalked anurans. “

“This new discovery suggests that a biphasic life cycle in which filter-feeding tadpoles live in aquatic, ephemeral environments was already present in the early evolutionary history of sessile anurans, and that at least 161 million It has been shown to remain stable over the years.”

of findings Published in this week’s magazine nature.

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M. Chubar others. The oldest tadpoles reveal the evolutionary stability of anuran life cycles. naturepublished online October 30, 2024. doi: 10.1038/s41586-024-08055-y

Source: www.sci.news

Science discovers oldest known tadpole fossil dating back 161 million years.

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Scientists discovered fossils in Argentina’s Santa Cruz province

Mariana Chubar et al., Journal (2024)

The beautifully preserved fossilized tadpoles are the oldest discovered by science, dating back 161 million years, and their anatomy is strikingly similar to some of today’s species. I am.

Paleontologists discovered the fossil in January 2020 while searching for feathered dinosaurs in Argentina’s Santa Cruz province.

“They missed the mark,” says Mariana Churivar of Universidad Maimonides in Buenos Aires, Argentina. “But after many days of digging, one of our team members discovered a stone with a special signature: a fossilized tadpole.”

Chubar and her colleagues have now identified this tadpole as belonging to an extinct frog species. Notobatrachus degiustoiwas deciphered from hundreds of adult specimens discovered in the same fossil deposit since 1957.

Until now, scientists had never unearthed tadpole fossils from before the Cretaceous period, which began about 145 million years ago. This specimen is also the first fossil tadpole from an early frog lineage known as stalk anurans, which is older than modern species known as crown anurans.

This fossil is very well preserved, with eyes and nerves visible in the head, forelimbs, and part of the tail. The researchers estimate that it was about 16 centimeters long, comparable to the largest tadpole in existence today.

The part of the skeleton that supports the gills suggests that the specialized filter-feeding anatomy of modern tadpoles had already evolved in this fossilized tadpole, Chubar said.

The similarities between ancient and modern tadpoles are so great that the researchers were even able to determine the developmental stage in the fossils, concluding that they were just about to undergo metamorphosis into frogs.

Illustration of tadpoles and adults of the species Notabatrachus degiustoi

Gabriel Rio

Earth’s warm, humid climate in the past, combined with the lack of competition and predation from other frog species and fish, may have made it easier for tadpoles to grow large, Chubar said.

Jody Lowry The Australian Museum in Sydney said the discovery of the oldest known tadpole “confirms how successful and stable the ‘typical’ frog life cycle we all learn about in school is.”

The size of the tadpoles tells us a lot about the habitat in which frogs evolved more than 160 million years ago, a water-rich environment with few predators or competitors, she says. “This is something modern frog species can only dream of.”

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Source: www.newscientist.com