Fish that have skeletons consisting of hard rubber-like cartilage rather than bone are members of the class Chondrichthyes. Compared to most other land mammals, humans are relatively hairless, but they have far more sweat glands. After birth, they are provided with protein and fat rich milk to eat and are usually protected until maturity. In the case of both reptiles and birds, the eggs are fertilized within the reproductive tract of females. This broad range of useful features has made mammals highly adaptive and successful. Salamander and frog class Amphibia.
Braylee. Age: 29.
Three of the vertebrate classes are fish.
Zaria. Age: 23.
Anthro 3D models
Their bodies took the amniote egg revolution of reptiles and birds one step further. In contrast, endothermic animals are able to remain active at night and often in the winter when the air temperatures are especially cold. Tuna, bass, salmon, and trout are examples of Osteichthyes. Young mammals spend a long period of their early development within their mother's uterus.