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Key to decapodiform Cephalopod families

Arms

  • Arms I-III: Maximum number of armature series
    • 2
    • 3
    • 4
    • 5 or more
  • Arms I-III: Hooks
         Absent Present

  • Arms IV: Size
    • Much smaller than other arms (coded from here on as 'smaller')
    • Somewhat similar to other arms (coded from here on as 'similar')
    • Much larger than other arms (coded from here on as 'larger')

Buccal crown

  • Position of connectives to arms IV
         Dorsal Ventral

  • Suckers
         Absent Present

  • Number of supports
    • 6
    • 7
    • 8

Eyes

  • Cornea
         Absent Present

  • Position
         Sessile Stalked

  • Size
         Small, much smaller than head Normal, same size as head

  • Secondary eyelid
         Absent Present

Fins

  • Free anterior lobes
         Absent Present

  • Free posterior lobes
         Absent Present

  • Position
         Terminal Normal Sub-terminal

  • Size
         Small Intermediate Large

  • Fin shape )
    • Circular-elliptical
    • Sagittate
    • Lanceolate
    • Ear-shaped
    • Ribbed
    • Rhomboid
    • Lobate
    • Skirt-like
  • Attachment to mantle muscle
         No Yes

Funnel

  • Locking-apparatus
    • Straight
    • Inverted-T shaped
    • Lazy-T shaped
    • Oval
    • Oval with tragus and/or antitragus (from here on referred to as 'Oval-bumpey')
    • Triangular
    • Fused
    • Boomerang
    • Keyhole
  • Lateral funnel adductor muscle
         Absent Present

Head

  • Elongate shape
         Absent Present

Mantle

  • Dorsal connection to head
         Broad Fusion Nuchal-lock Fusion Free

  • Large scales, tubercles or pads
         Absent Present

Photophores

  • Many on mantle, head: Absent Present
  • On viscera: Absent Present
  • On/in tentacles: Absent Present
  • On eyeballs: Absent Present
  • On funnel: Absent Present

Tail

  • Tail long and slender
         Absent Present

Tentacles

  • Existence
         Absent Present

  • Number of armature series on clubs
    • None
    • 2
    • 3
    • 4
    • 6
    • Non-uniform series
  • Club keel
         Absent Present

  • Hooks
         Absent Present

  • Carpal locking apparatus
         Absent Present

  • Thickness at base much greater than base of arm III
          No Yes



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