Differences do exist. Anurans are all obligate metamorphs - all tadpoles will eventually undergo the change to frog or toad. Amphibians evolved from fish in the late Devonian era, giving Earth its first land dwelling vertebrates.
Recent theories are that salamanders developed well before the tailless frogs and toads.
Salamanders developed from the Labrynthodonts, the first vertebrates to venture onto land in the Devonian period, over 350 million years ago. The first fossil salamander to be discovered was found in Germany in 1725, but was misidentified at the time as the skeleton of a human who had perished in Noah's flood. It has recently been dated to the Miocene period, about 15 million years ago, and given the name Andrias scheuchzeri . The earliest recognized salamander was a 7-inch skeleton found in Kazakhstan in the former USSR, and named Karaurus . It dates to the late Jurassic period, about 140 million years ago.