Dichotomous Key/Hexanchiformes

1

 * Tissue on gill slits
 * Protruding - Chlamydoselachus anguineus
 * Not protruding -

2

 * Number of gills
 * Six -
 * Seven -

3

 * Number of pups in one litter
 * 22 to 108 - Hexanchus griseus
 * 13 or less - Hexanchus nakamurai

4

 * Spots
 * Present - Notorynchus cepedianus
 * Absent - Heptranchias perlo