Class Chondrichthyes

1. Class Chondrichthyes Kingdom: Animalia Phylum: Chordata Subphylum: Vertebrata Class: Chondrichthyes Subclass: Holocephali Subclass: Elasmobranchii SuperorderBatoidea SuperorderSelachimorpha

2. Cartilaginous Fish • Includes: • Sharks • Rays • Skates • Ratfish/Chimeras/Ghost fish

3. General Characteristics: • Jawed fish • Skeleton made of cartilage • Lack swim bladder • Teeth & vertebrae sometimes calcified

4. General Characteristics: • Possess movable jaws • Mouth is ventral, underneath the head • Countershading – the ventral sides are light colored while the dorsal sides are darker creating a simple camouflage

5. Evolution: • Earliest relatives found in the Devonian Age • Modern looking sharks first appear in the Jurassic Era

6. Evolution • Megalodon • Ancient Shark • Largest predatory fish ever • Twice the size of a Great White

7. Subclass Holocephali • Includes: Ratfish/Chimeras • Deep water fish • Large head & eyes • Gill slits covered by a flap of skin • No scales, skin instead • Caudal fin developed into “rat-like” tail • Eats crustaceans & mollusks

8. Subclass Elasmobranchii • Includes: Sharks, Rays, & Skates • Denticles – streamlined scales made of the same material as their teeth

9. Energy Efficiency: • Cartilage skeleton make them lighter, thus takes less energy to remain buoyant • Buoyant oils in liver • Fins at angles to provide lift • Skin elasticity transfers energy to tail • Scales reduce friction (smooth towards tail, rough towards head) • Store urea to maintain similar density to water

10. SuperorderBatoidea • Includes: Skates, Rays, & Sawfish • Flattened body • Demersal – live on the ocean floor • Gill slits on ventral (bottom) side

11. Skates & Rays • Pectoral fins are flat and expanded • Head fuses with pectoral fins with eyes on top

12. Skates vs. Rays

13. Stingrays • Equipped with a stinging spine • Spine connected to venomous glands • Teeth modified into grinding plates

14. Manta & Devil Rays • Not bottom dwellers instead choose to swim

15. Sawfish vs. Sawshark • Sawfish categorized with the rays while sawshark categorized with the sharks • Sawfish have ventral gill slits, smaller and flatter body • Sawshark have gill slits on the side, rounded body, bigger overall, and presence of barbels

16. SuperorderSelachimorpha • Includes: Sharks • Gill slits on the side • Paired & unpaired fins • Most are quite mobile and designed for fast swimming

17. Paired vs. Unpaired fins • Paired: Pectoral & Pelvic • Comparable to our arms and legs • Unpaired: 1st Dorsal, 2nd Dorsal, Anal, and Caudal • All found along mid-line

18. Scales • Scales are very small and sharp • Same composition as the teeth

19. Jaws • Made of bone • Contain the disposable teeth • In some species capable of extending jaw out from body

20. Teeth • Same composition as the scales • Continually shed and replaced by the rows behind

21. Respiration • Must swim to force water through their gills • Some such as nurse sharks can get enough oxygen so they do not need to swim (pumping mechanism) • Sharks that do not have this mechanism go through active periods and rest periods where they lower body functions

22. Digestion • Very short esophogus • Stomach can be up to 1/3 the length of the shark • Intestine is really small, only about a foot

23. Nervous System • Lateral line used for sensing vibrations in the water

24. Nervous System • Ampullae of Lorenzini • Jelly filled canals that can detect electrical fields, magnetic fields, temperature, salinity, water pressure, etc. • Electroreception

25. Nervous System • Paired external nostrils that lead directly to the brain • Very acute sense of smell, can detect concentrations as low as one part per billion

26. Shark Classification • Two Sub-Orders: • Galeomorphs & Squalomorphs • Further broken down into orders

27. Order Heterodontiformes: • Bullhead Sharks • Pig like snout • Bottom dwellers

28. Order Orectolobiformes: • “Carpet Sharks” • Very short mouths • Upper lobe of caudal fin extended with reduced lower lobe • Includes filter feeders

29. Order Lamniformes: • “Mackerel Fish” • Larger front teeth • Include some of most popular • Most are active predators • Functionally warm-blooded

30. Order Lamniformes: • “Goblin Sharks” • Mitsukurindidae • “Sandtiger Sharks” • Carchariidae

31. Order Lamniformes: • “Ragged-Tooth Sharks” • Odontaspididae • “Thresher Sharks” • Alopiidae

32. Order Lamniformes: • “Megamouth Shark” • Megachasmidae • “Crocodile Sharks” • Pseudocarchariidae

33. Order Lamniformes: • “Basking Shark” • Cetorhinidae • “Mackerel Sharks” • Lamnidae

34. Order Carcharhiniformes: • “Ground or Whaler Sharks” • Adaptable to many environments, even estuarine and freshwater • Flappable lower eyelids

35. Order Carcharhiniformes: • “Whaler Sharks” • Carcharhinidae • “Hammerhead Sharks” • Sphyrnidae

36. Order Carcharhiniformes: • “Cat Sharks” • Schliorhinidae

37. Order Chlamydoselachi • “Frilled Shark” • Eel like body • Teeth are three pronged • Deep water

38. Order Hexanchiformes • “Cow Sharks” • Deep water • Very little is known

39. Order Echinorhiniformes • “Bramble Sharks” • Thick tail stalk • Has bumps on skin • “hedgehog shark

40. Order Sqauliformes • “Dogfish Sharks” • Large ranges of sizes • Generally best known shark

41. Order Sqauliformes • Greenland Shark (21 feet +) • Dwarf Laternshark

42. Order Squantiniformes • “Angel Sharks” • Flattened bodies • Gills on ventral side • Mouth at end rather than ventral like rays and skates

43. Order Pristiophoriformes • “Sawsharks’ • Similar to sawfish, but skinnier and have sensitive barbs on snout • Alternating long short teeth