Amblycranium variabile was named by Ross (1951) [Paratypes: YPM 18019, 18021, 18022]. Its type specimen is YPM 18020, a cephalon/head (cranidium), and it is a 3D body fossil. Its type locality is Locality 5, Hillyard's Canyon, Zone "E", which is in a Stairsian shallow subtidal limestone in the Garden City Formation of Idaho. It is the type species of Amblycranium.