Scientists from Argentina have discovered the oldest tadpole in the world, which coexisted with dinosaurs in the Middle Jurassic approximately 161 million years ago. This paleontological finding is crucial for understanding the evolution of frogs and toads.
The fossil, found in Argentine Patagonia, is exceptionally well-preserved, allowing researchers to conclude that the morphology of tadpoles has remained virtually unchanged for the last 160 million years.
“Not only is it a significant discovery due to its antiquity, but it is also a unique tadpole due to the preserved characteristics,” commented Mariana Chuliver, a researcher at the Fundación Azara and lead author of the study recently published in the journal Nature.
Chuliver added that the preservation of this specimen is extremely rare, as tadpoles, with their soft bodies, have few opportunities to fossilize.
“Soft tissue remains have been preserved, such as nerves and eyes, in addition to a fundamental feature: the hyobranchial skeleton, which is the cartilage that supports a tadpole’s gills. This is important because it allows us to understand the feeding and lifestyle of these organisms,” she explained.
The 16-centimeter fossil was discovered on a ranch in the province of Santa Cruz, about 2,300 kilometers south of Buenos Aires, in January 2020 while searching for dinosaur remains.
“This tadpole is remarkable because through an analysis of various morphometric variables, we were able to determine that it is a giant tadpole. The adult of this species measured approximately 15 centimeters long, including the tail,” Chuliver noted.
The expert, who led the work alongside the Fundación Azara, the Museum of Natural Sciences, and the Chinese Academy of Sciences, pointed out that the fossil record of tadpoles is very limited and that this specimen belongs to Notobatrachus degiustoi, an ancestral species of modern anurans, a group that includes frogs, toads, and salamanders.
“This new finding, which places the origin of amphibian larvae very close to the group of current anurans, reveals that the morphology of tadpoles has remained almost unchanged for the last 160 million years,” Chuliver affirmed.
“Therefore, it is not only the oldest tadpole in the world, with exceptional preservation, but it also provides us with information about the size of one of the few known frog species of that time,” she concluded.
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