How long have amphibians been on earth?

Tetrapods (early amphibians) emerged in the fossil record some time int he lower Carboniferous, around 360 million years ago. Reptiles emerged later in the carboniferous, 320-310 million years ago, and were probably the dominant terrestrial fauna by the start of the Permian, 299 million years ago. If any period in geological history could be described as the age of the amphibians, it would be the lowere-to-middle Carboniferous.