Vieraella is an extinct genus of frog from the Jurassic period. It was about 3 cm long.
Vieraella was the first true frog, as the older Triadobatrachus still featured many primitive characteristics. Its anatomy was highly similar to that of modern frogs.
References
Estes, R., and O. A. Reig. 1973. The early fossil record of frogs: a review of the evidence. Pp. 11-63 In J. L. Vial (Ed.), Evolutionary Biology of the Anurans: Contemporary Research on Major Problems. University of Missouri Press, Columbia.