Amphibians are a group of tetrapod vertebrates that include modern-day frogs and toads, caecilians, and newts and salamanders. The first amphibians evolved from lobe-finned fishes approximately 370 million years ago during the Devonian Period. They were the first vertebrates to make the move from life in water to life on land. Despite their early colonization of terrestrial habitats, most lineages of amphibians have never fully severed their ties with aquatic habitats. In this article, we'll take a look at six groups of amphibians, their characteristics and the organisms that belong to each group. Newts and salamanders diverged from other amphibians during the Permian Period (286 to 248 million years ago). Newts and salamanders are slender-bodied amphibians that have a long tail and four legs. Newts spend most of their life on land and return to water to breed. Salamanders, in contrast, spend their entire lives in water. Newts and salamanders are classified into about ten families, some of which include mole salamanders, giant salamanders, Asiatic salamanders, lungless salamanders, sirens, and mudpuppies.