The oldest tadpole fossil ever has been found—and it’s a big one. The discovery in Patagonia shows that frogs have had a tadpole stage for at least 160 million years.

A new paper in the journal Nature details the oldest known tadpole fossil. Ringing in 20 million years earlier than scientists previously had evidence of, this fossil might get us closer to an answer.

The tadpole was about 6 inches (16 centimeters) long — like a baseball with a 3-inch-long (7.6 cm) tail. The adult frog is just as big, which surprised the researchers.