What is "vieraella"

Vieraella is an extinct genus of frog from the Jurassic period of Argentina, and the oldest true frog known.

Despite living around 200 million years ago, Vieraella was anatomically very similar to modern frogs. For example, its hind legs were adapted for jumping, and the skull already possessed the lattice-like form found in modern species. It was, however, an unusually small frog, measuring only in length. Although older frog-like creatures are known, such as Triadobatrachus, these possessed many primitive characteristics, and cannot be said to be "true" frogs.