Knightoconus
| Knightoconus | |
|---|---|
| |
| artistic reconstruction of Knightoconus antarcticus | |
Scientific classification 
| |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Mollusca |
| Class: | Monoplacophora |
| Order: | †Archinacelloidea |
| Genus: | †Knightoconus Yochelson et al., 1973[1] |
| Species: | †K. antarcticus
|
| Binomial name | |
| †Knightoconus antarcticus Yochelson et al., 1973[1]
| |
Knightoconus antarcticus is an extinct species of fossil monoplacophoran from the Cambrian Minaret Formation of Antarctica.[1] It is thought to represent an ancestor to the cephalopods. It had a chambered conical shell, but lacked a siphuncle.[2]
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.[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] Unlike monoplacophoran fossils, there is no evidence of muscle scarring in Knightoconus fossils.[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.[6]
An alternate taxonomy is:
See also
- Evolutionary history of cephalopods
- Plectronoceras
References
- ^ .
- ISBN 9780632060481.
- S2CID 128629737.
- ^ S2CID 128682549.
- ISBN 978-0-521-40242-2.
- ISBN 978-0-8137-1170-6.
- ^ "The Paleobiology Database". Retrieved 6 August 2009.