Class Cepalophoda

• • head foot
  • 600 extant; ammonites extinct
  • Fast-moving, active carnivores
  • EXCLUSIVELY marine
  • Largest cephalopod is the giant squid Architeuthis
  • Derivatives of the molluscan foot are the siphon/funnel, arms (8) and tentacles (2)
  • Possess two eyes with cornea, lens, iris, diaphragm and retina thus focusable and image-forming
  • Closed circulatory system with systemic and branchial hearts
  • Locomotes by jet propulsion
• Subclass Nautiloidea

  • Nautilus
  • possessing true shell
  • shell divided by septa
  • septa penetrated by siphuncle (calcified tube with enclosed strand of vascularized tissue)
  • cameral fluid in chambers
• Subclass Coloidea

  • chromatophores (colored cells) overlay iridocytes (reflective cells)
  • photophores
  • ink sac discharged through anus
  • male octopi have hectocotylized arms