Problem 8

Background and context

Fishes belong to the subphylum vertebrata under the phylum Chordata.The vertebrates can be divided into two parts that is agnatha and gnathostomata. Under the gnathostomata fishes present which are mainly categorized into chondrichthyes (cartilaginous fish) and osteichthyes (bony fish). Chondrichthyes are descended from the placoderms which have a endoskeleton of bones.