A vertebrate is an animal with a spinal cord surrounded by cartilage or bone. The vertebrates are also characterized by a muscular system consisting primarily of bilaterally paired masses and a central nervous system partly enclosed within the backbone. The 7 classes of vertebrates are: Class Aves, Class Reptilia, Class Agnatha, Class Amphibia, Class Mammalia, Class Osteichthyes, Class Chondrichthyes.