2. The unique characteristics is the presence of the mammary glands. They bring forth their young alive. They feed their young with their milk from the mammary glands. Their bodies are covered with hair and fur. 3. They live in water, their bodies are usually covered with scales. They are able to breathe in water because they have gills. They used their fins to be able to swim in water. 4. Animals that spend their life both in water and land. They have smooth, moist and scale less skin. 5. Are terrestrial animals, they have dry scaly skin.
