Dichotomous Key/Cephalopoda

1

 * External shell
 * Present - ../Nautiloidea/
 * Not present - 2

2: Coleoidea

 * Modified (or lost) arm pair
 * Arm pair IV - 3
 * Arm pair II - 4

3: Decapodiformes

 * Cornea
 * Present - 6
 * Not present - 5

4: Octopodiformes

 * Photophores
 * Present - Vampyroteuthis infernalis
 * Not present - ../Octopoda/

5

 * Shell shape
 * Horn-shaped - Spirula spirula
 * Other or not present - 7

6: Sepioidea

 * Cuttlebone
 * Present - ../Sepiidae/
 * Not present - 8

7

 * Gladius
 * Present - ../Oegopsida/
 * Not present - 10

8: Sepiolida

 * Depressions on funnel locking-apparatus
 * One - ../Sepiolidae/
 * Two, or apparatus fused - ../Sepiadariidae/

9

 * Adhesive organ on dorsal surface of mantle
 * Present - ../Idiosepiidae/
 * Not present - ../Myopsida/

10

 * Branchial canals in gills
 * Present - 11
 * Not present - 9

11: Bathyteuthoida

 * Buccal connectives attaching to border of arms IV
 * Dorsal border of arms IV - ../Bathyteuthidae/
 * Ventral border of arms IV - ../Chtenopterygidae/

cs:Dichotomický klíč:Cephalopoda