Plectronoceras
| Plectronoceras Temporal range: Upper Cambrian |
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Scientific classification  |
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| Kingdom: | Animalia |
| Phylum: | Mollusca |
| Class: | Cephalopoda |
| Order: | †Plectronocerida |
| Family: | †Plectronoceridae |
| Genus: | †Plectronoceras Ulrich & Foerste, 1933 |
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Plectronoceras is the earliest known shelly cephalopod, dating to the Upper Cambrian.[1] Its 14 known specimens hail from the basal Fengshan Formation (north-east China) of the earliest Fengshanian stage.[2] None of the fossils are complete, and none show the tip or opening of the shell.[2] Approximately half of its shell was filled with septa; 7 were recorded in a 2 cm shell.[3] Its shell contains transverse septa separated by about half a millimetre, with a siphuncle on its concave side.[2] Its morphology matches closely to that hypothesised for the last common ancestor of all cephalopods.[2]
Plectronoceras is the type genus of the family Plectronoceratidae.
References
- ^ Dzik, J. (1981). "Origin of the cephalopoda". Acta Palaeontologica Polonica 26 (2): 161–191.
- ^ a b c d Clarke, M.R.; Trueman, E.R. (1985), "Main features of cephalopod evolution", in Wilbur, Karl M.; Clarke, M.R.; Trueman, E.R., The Mollusca, 12. Paleontology and neontology of Cephalopods, New York: Academic Press, ISBN 0-12-728702-7
- ^ Webers, G. F.; Yochelson, E. L. (1989). "Late Cambrian molluscan faunas and the origin of the Cephalopoda". In Crame, J. A. Origins and Evolution of the Antarctic Biota 47. Geological Society, London: Special Publications. p. 29. doi:10.1144/GSL.SP.1989.047.01.04.
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