Taxonomic debate
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. The prevailing argument suggests that a strand of tissue remained attached to the previous septum as the mollusc moved forwards and deposited its next septum, stopping that new septum from closing completely and becoming mineralised itself. 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. Unlike monoplacophoran fossils, there is no evidence of muscle scarring in ''Knightoconus'' fossils. Scars from the closely related ''Hypseloconus'' have been used to determine its orientation. ''Knightoconus'' started life with an