Cartilaginous Fishes Cartilaginous fishes (Chondrichthyes) have a skeleton made not of bone, but of cartilage, which is lighter and more flexible than bone Cartilaginous fishes have well-developed jaws and paired fins for efficient swimming Most cartilaginous fish also have rough, sandpaper-like skin, the result of placoid scales pointed tip directed backwards

Cartilaginous Fishes Cartilaginous fishes include sharks, skates, rays and chimeras, or ratfishes Nearly all are marine ~350 species of sharks; ~500 species of skates and rays; 30 species of chimeras

Sharks (cue scary, cello music) Sharks are often referred to as living fossils because many of the species alive today are similar to ones that swam the seas >100 million years ago Sharks have powerful jaws with rows of numerous sharp, often triangular teeth – Lost or broken teeth are quickly replaced by another, which shifts forward from the row behind it as if on a conveyor belt

Sharks Sharks have fusiform, spindle-shaped bodies, which cut easily through the water A well-developed, muscular caudal fin propels them through the water; paired pectoral fins enable steering and dorsal fins provide stability

Sharks are efficient predators Many sharks exhibit counter-shading, appearing dark on top and light on the bottom – Camouflage from above and below Why? flmnh.ufl.edu

Rays and Skates Rays and skates have dorsoventrally flattened bodies, with 5 pairs of gill slits on the underside (ventral side) of their body Most are demersal, spending much of their lives on the sea floor Pectoral fins are greatly extended resembling wings

Is it a ray, or a skate? Skates usually have 2 dorsal fins; Rays lack dorsal fins altogether Skates have a muscular tail; Rays have a whip- like tail, usually with a prominent stinger Ray Skate

Chimeras, or ratfishes Approximately 30 species of deep-water, strange-looking cartilaginous fish are grouped separately as chimeras, or “ratfishes” Only one pair of gill slits, covered by a flap of skin Demersal (bottom-dwelling) Some with a long, rat-like tail