ZOOLOGY SUPERCLASS- PISCES CLASS - CHONDRICHTHYES
SUPER CLASS PISCES :- CLASS CHONDRICHTHYES :- ( CARTILAGINOUS FISHES ) NATURAL HISTORY Skeleton is made of cartilage. Most sharks and rays are marine, but a few live in tropical rivers above salt water. Sharks live in open water, and rays on the bottom. The sharks are predaceous, active swimmers and feed on small fishes. Sharks and rays are used as human food in many countries. Shark liver contains much oil rich in vitamin A. Sharks are also a nuisance to fishermen, because they tear nets and steal captured fishes. Large sharks may capsize small boats and injure or kill fishermen. Living fishes probably exceed 20,000 species, an abundance and diversity unequalled among all other vertebrates. They originated 530 million years ago allowing vast span of time for evolutionary divergence and for origin and extinction of major phyletic lines. SCOLIODON (DOGFISH) :- CLASSIFICATION Phylum .............. Chordata Group ........