Salamanders and newts comprise the order of amphibians known as the Urodela (or Caudata). They typically have elongated bodies, long tails and two pairs of legs of roughly similar size, although some forms have lost one pair of limbs. They thus resemble more closely the earliest fossil amphibians in terms of overall body shape than any other present-day group.
Salamanders and newts live in a variety of habitats and include fully aquatic and fully terrestrial forms, as well as species that divide their time between water and land. Aquatic forms are found in rivers, lakes, mountain streams, ponds, swamps and underground caves. Terrestrial species burrow deep into the soil and some may climb to considerable heights in trees. Because salamanders and newts have a skin that is permeable to water, they cannot tolerate hot, dry conditions and, for many species, the summer is a time when they retreat into damp refuges, emerging only on cool nights.
The term "salamander" derives from the Latin Salamandra, in turn derived from the Greek for "fire-lizard." Salamanders were associated with fire because they crawled out of logs thrown onto the fire and it was thought they could crawl through fire. "Salamander" is applied generally to any tailed amphibian, but more especially to those with terrestrial habits. The term "newt," derived from the Anglo-Saxon evete which became ewt, refers only to the European genus Triturus and the North American genera Taricha and Notophthalmus, all animals that return to water each spring to breed.Red Hills Salamander
In common with most other amphibians, salamanders and newts have a smooth, flexible skin that lacks scales and is usually moist. The skin acts as a respiratory surface at which oxygen enters the body. For this reason, salamanders and newts are restricted to damp or wet habitats. The outermost layer of the skin is frequently shed. In some species it comes off in bits and pieces, in others it peels off in one piece. The shed skin is usually eaten but sometimes a complete skin can be found hanging from water weed.
All salamanders and newts are carnivores, feeding upon small, living invertebrates, such as insects, slugs, snails, and worms. They possess a tongue which is used to moisten and move food in the mouth; in some species it can be flicked some distance forward to capture small prey. The tail is well developed for swimming in many species, and may bear a dorsal fin. The two pairs of limbs have digits.
The eggs of tailed amphibians do not have shells, but are coated with layers of protective jelly. Usually, the egg hatches into a wholly carnivorous larva, which grows until it metamorphoses into the adult form. Metamorphosis involves a number of complex changes which equip the salamander or newt for its adult life.
In the amphibious life cycle, the adult spends most of its life on land. The moist skin of newts and salamanders is, for most species, only one route by which oxygen and carbon dioxide enter and leave the body. Typically, larvae have external gills and adults have lungs. Some species, including both aquatic and terrestrial forms, also use the inner surfaces of their mouths, rhythmically sucking in and expelling water or air through the mouth or nostrils. This "buccal pumping" is very apparent as rapid vibrations of the soft skin under a newt's or salamander's chin. It serves not only as a respiratory mechanism but also enables the animal continually to sample its external environment for odors.