Clownfish lacks both of them and hence, cannot be classified as a mammal. One more reason for clownfish not being a mammal is the fact that it reproduces by laying eggs, a biological trait that is surely not found in most mammals.
Mammals are animals that have fur, produce milk for their young and have a backbone. These animals also may make sound or try to communicate with the other animals. They may yell or scream. Mammals can be either carnivores, herbivores or both. Some of the smarter animals are found in this classification of animals. The primates are considered to be intelligent. Rats are also very smart.
They are also one of the largest type of animals as well. The blue whale is considered an animal even though it swims in the ocean. It has all of the characteristics that makes a mammal. They are the largest animal in the world. Even though the blue whale is a mammal, not all marine animals are mammals. The clown fish is not.