| Plectronoceras Temporal range: Cambrian
| |
|---|---|
| |
| Life reconstruction of Plectronoceras cambria | |
Scientific classification 
| |
| Kingdom: | Animalia |
| Phylum: | Mollusca |
| Class: | Cephalopoda |
| Subclass: | Nautiloidea |
| Order: | †Plectronocerida |
| Family: | †Plectronoceridae |
| Genus: | †Plectronoceras Ulrich & Foerste, 1933 |
| Species | |
| |
Plectronoceras is the earliest known shelled cephalopod, dating to the Late Cambrian.123 None of the fossils are complete, and none show the apex or aperture of the shell.3 Around half of its shell was filled with septa; 7 were recorded in a 2 centimetres (0.79 in) shell.4 Its shell contains transverse septa separated by about half a millimetre, with a siphuncle on its concave side.3 Its morphology matches closely to that hypothesised for the last common ancestor of all cephalopods.3
Plectronoceras is the type genus of the family Plectronoceratidae. Fossils of Plectronoceras have been found in the San Saba Limestone of Texas and in Yunnan, China.2
Species
- †Plectronoceras cambria (Walcott, 1905)
- †Plectronoceras exile (Flower, 1964)
- †Plectronoceras gracile (Flower, 1964)
- †Plectronoceras huaibeiense (Chen & Qi, 1979)
- †Plectronoceras liaotungense (Kobayashi, 1935)
References
References
- Dzik, J. (1981). "Origin of the cephalopoda" (PDF). Acta Palaeontologica Polonica. 26 (2): 161–191.
- Plectronoceras at Fossilworks.org
- Clarke, M.R. (1985), "Main features of cephalopod evolution", in Wilbur, Karl M.; Clarke, M.R.; Trueman, E.R. (eds.), The Mollusca, vol. 12. Paleontology and neontology of Cephalopods, New York: Academic Press, ISBN 0-12-728702-7
- Webers, G. F.; Yochelson, E. L. (1989). Crame, J. A. (ed.). "Late Cambrian molluscan faunas and the origin of the Cephalopoda". Geological Society, London, Special Publications. 47 (1): 29–42. Bibcode:1989GSLSP..47...29W. doi:10.1144/GSL.SP.1989.047.01.04.