Lissamphibia are classified by characteristics of tooth, skin, and body structure. The most abundant family, containing about 200 known species of salamanders, is the Plethodontidae. Evolved in the Appalachian Mountains of the United Sates, it has many species throughout North America, a group of species that has invaded central america and radiated extensively, and two species in Europe. The skin is usually smooth and moist and devoid of scales or external ear openings. They are brightly colored, often brown, black, yellow, or red, and often have light or dark spots, bars, or stripes.
Salamanders are deaf to airborne sounds but hear or feel by sensing vibrations from the ground.
They have relatively good vision but have little or no voice production. Salamanders have a keen sense of smell and taste largley attributed to their sensitive tounges, packed with various types of nerve endings. Their mouths contain small teeth implanted on the margins of the upper and lower jaws and in some cases the roof of the mouth. The skin contains many glands, some secreting mucus to help maintain moisture and others secreting a toxic or irritating substance when the animal is frightened. Salamanders molt their skin, from every few days to every few weeks, depending on the species and except in very cold weather, when it ceases completely.