KINGDOM ANIMALIA Phylum Chordata Subphylum Vertebrata Class Chondrichthyes

Class Chondrichthyes 846 species of sharks and rays Date to over 400 mya Cartilaginous endoskeleton Jawed Well-developed pectoral/pelvic fins, powerful tail fin Skin is rough due to numerous placoid scales (constantly worn out/replaced)

Class Chondrichthyes Teeth = enlarged placoid scales Teeth form in actively growing skin areas in mouth just behind upper/lower jaws; skin grows, teeth pushed over edge of jaw and increase in size Teeth worn = reabsorbed or lost In rays, teeth fuse to form bony plates

Class Chondrichthyes Internal fertilization facilitated via unique pelvic claspers on males Anamniote eggs encapsulated in leathery case or retained in body until birth of living young

Class Chondrichthyes 2 informal groups: differ in body plan and dentition 1. Sharks (359 species) – powerful swimmers – mid-water dwelling – solitary predators 2. Rays (456 species) – dorsoventrally flattened, enlarged pectoral fins- subject to waves of muscular contraction – bottom-dwelling – eat shelled inverts (crush)

Class Chondrichthyes Most marine, some taxa are estuarine or freshwater (28 species) Range in size (from 20 cm to over 12 m) Commercially important in food, cosmetic, pharmaceutical, and medical products Estimated 771,400 tons of sharks/rays harvested each year by humans (while only 30 humans-2.6 tons harvested by sharks)