Salamanders are amphibians with tails. The amphibians evolved from lobe-finned fishes that made the transition to land. They inhabit only freshwater environments, not marine environments. Some primitive amphibians retain gills into adulthood, and some advanced amphibians have gills only in the larval stage, but have simple lungs as adults. All amphibians also retain some ability to obtain oxygen directly through their permeable skins, as long as the skin remains moist. Today there are are about 700 species of salamanders. That includes primitive salamanders such as the giant and Asiatic salamanders (67 species), the advanced salamanders (615 species), and a small group called sirens (4 species).

Of the advanced salamanders, the true salamanders and newts account for about 113 species. These advanced salamanders begin life hatching from gelatinous masses of eggs in freshwater, go through an aquatic larval phase, then move onto land. On land, they usually seek moist places, hiding during the day and emerging to feed at night. When the eastern newt emerges onto land, it is bright red-orange with orange spots, and is called a “red eft”. While many salamanders remain on land, the eastern newt returns to fully aquatic life after several years. When it does, it undergoes physical changes including a dark greenish skin color and development of fins along the tail. Having lungs, it periodically rises to the surface of the water to breathe, or occasionally crawls out onto branches lying in the water.

There are about 32 species of mole salamanders, including the yellow-spotted salamanders. These spend most of their adult life underground, emerging only to travel across land to lay their eggs in freshwater locations.

Most of the advanced salamanders (450 species) remain lungless, relying only on the absorption of oxygen through their skins. The red-backed and two-lined salamanders are two examples of lungless salamanders in New England.