Knightoconus

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Extinct genus of molluscs

title: "Knightoconus" type: doc version: 1 created: 2026-02-28 author: "Wikipedia contributors" status: active scope: public tags: ["prehistoric-monoplacophorans", "cambrian-molluscs", "paleozoic-antarctica", "prehistoric-animals-of-antarctica", "fossil-taxa-described-in-1973"] description: "Extinct genus of molluscs" topic_path: "general/prehistoric-monoplacophorans" source: "https://en.wikipedia.org/wiki/Knightoconus" license: "CC BY-SA 4.0" wikipedia_page_id: 0 wikipedia_revision_id: 0

::summary Extinct genus of molluscs ::

| fossil_range = Dresbachian ~ | image = Knightoconus_reconstruction.png | image_caption = Artistic reconstruction of Knightoconus antarcticus | parent_authority = Yochelson et al., 1973 | taxon = Knightoconus antarcticus | authority = Yochelson et al., 1973

Knightoconus antarcticus is an extinct species of fossil monoplacophoran from the Cambrian Minaret Formation of Antarctica. It is thought to represent an ancestor to the cephalopods. It had a chambered conical shell, but lacked a siphuncle.

Taxonomic debate

The absence of a siphuncle in K. antarcticus has been taken as evidence against its being an ancestor of cephalopods, 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 exogastric shell that became endogastric as the organism grew.

An alternate taxonomy is: Tergomya: Kiringellida: Hypseloconidae.

References

References

  1. (1973). "The bearing of the new Late Cambrian monoplacophoran genus ''Knightoconus'' upon the origin of the Cephalopoda". Lethaia.
  2. Boyle. (2005). "Cephalopods – ecology and fisheries".
  3. (1987). "The nautiloid cephalopods: A strange success". Journal of the Geological Society.
  4. (1989). "Origins and Evolution of the Antarctic Biota". Geological Society.
  5. {{Peel 1991
  6. (1992). "Geology and Paleontology of the Ellsworth Mountains, West Antarctica". Geological Society of America.
  7. "†''Knightoconus'' Yochelson et al. 1973". Paleobiology Database.

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prehistoric-monoplacophoranscambrian-molluscspaleozoic-antarcticaprehistoric-animals-of-antarcticafossil-taxa-described-in-1973