Knightoconus antarcticus is an extinct species of fossil monoplacophoran from the Cambrian Minaret Formation of Antarctica.

[2] The absence of a siphuncle in K. antarcticus has been taken as evidence against cephalopod ancestry, as factors that would allow a siphuncle to penetrate preexisting septal chambers remain unknown.

[3] Ten or more septa are found in mature individuals, occupying around a third of the shell – septa form very early and have been found in specimens as small as 2 mm in length.

[4] Scars from the closely related Hypseloconus have been used to determine its orientation.

[5] Knightoconus started life with an exogastric shell, that becomes endogastric as the organism grew.