Dichotomous Key/Octopoda

1

 * Cornea
 * Present - 2
 * Not present - 3

2: Incirrata

 * Detachable hectocotylus
 * Present - 5
 * Not present - 6

3: Cirrata

 * Secondary web
 * Present - 4
 * Not present - ../Opisthoteuthidae/

4

 * Shell shape
 * Saddle-shaped - ../Cirroteuthidae/
 * U-shaped - ../Stauroteuthidae/

5: Argonautoida

 * Tissue consistency
 * Gelatinous - 10
 * Muscular - 9

6

 * Eye shape
 * Tubular - ../Amphitretidae/
 * Other - 7

7

 * Eye shape
 * Laterally compressed - ../Bolitaenidae/
 * Other - 8

8

 * Eye shape
 * Rectangular - Vitreledonella richardi
 * Other - ../Octopodidae/

9

 * Web
 * Absent or greatly reduced except in four dorsal arms - ../Tremoctopodidae/
 * Consistent - 11

10

 * Web
 * Absent or greatly reduced except in four dorsal arms - Tremoctopus gelatus
 * Consistent - Haliphron atlanticus

11

 * Funnel locking-apparatus
 * Contains circular pit - ../Argonautidae/
 * Does not contain circular pit - Ocythoe tuberculata