KINGDOM ANIMALIA Phylum Chordata Class Chondrichthyes

1
KINGDOM ANIMALIAPhylum ChordataClass
Chondrichthyes
2
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)

3
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

4
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

5
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)

6
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)