Ancient banana-size tadpole was surprisingly about as big as its adult form.
Although frogs today start their lives as tadpoles, researchers have puzzled over when this two-stage lifestyle evolved.
Now, a remarkable 161-million-year-old fossil unearthed in Argentina in 2020 pushes back the evolutionary origin of tadpoles by at least 20 million years.
The specimen is “superbly preserved,” the authors report today in Nature
, including soft tissues that indicate it filtered its food from the water like modern tadpoles. Indeed, the fossil contained enough detail for them to determine it was a larval Notobatrachus degiustoi, a kind of froglike amphibian that lived alongside true frogs during the so-called “age of reptiles” some 252 million to 66 million years ago.
Experts tell The New York Times that the fossil is the first “solid and beautiful evidence” that tadpole-to-adult metamorphosis evolved very early in the group of amphibians that gave rise to Notobatrachus and its relatives, as well as modern frogs.
The ancient tadpole was huge—almost 16 centimeters long—which is slightly bigger than adults of the species that researchers have unearthed (as pictured above in an artist’s reconstruction).
Cases in which tadpoles are nearly as big or bigger than their adult forms are rare in frogs and toads today.
Source: Science.org
