''Paraplectronoceras'' is a genus of very early

nautiloid Nautiloids are a group of cephalopods (Mollusca) which originated in the Late Cambrian and are represented today by the living ''Nautilus'' and ''Allonautilus''. Fossil nautiloids are diverse and species rich, with over 2,500 recorded species. Th ...

s from the middle

Late Cambrian The Furongian is the fourth and final Epoch (geology), epoch and Series (stratigraphy), series of the Cambrian. It lasted from to million years ago. It succeeds the Miaolingian series of the Cambrian and precedes the Lower Ordovician Tremadocia ...

, named by Chen and Qi, 1979, type species ''Paraplectronoceras pyriforme'', for small, endogastrically curved forms found in the upper Yenchou and Wanwankou members of the Fengshan Formation of northeastern China. The shell of ''Paraplectronoceras'' is laterally compressed with the dorsal side somewhat more narrowly rounded than the ventral, and is moderately to rapidly expanded. The siphuncle is small, ventral in position, without calcareous deposits. Segments are slightly expanded, pearshaped in early stage. Septal necks are short, curved in early stage, but straight in the adult. Species of ''Paraplectronoceras'' along with another plectronoceratid, ''Lunanoceras longatum'', and the protacinocerid ''Wanwanoveras exigum'' have been found in Liaoning and Shandong provinces, in the lower part of the ''Changia Zone'', which is correlated with the earliest Trempealeauan of North America.Wen-tang Shang, Pei-ji Chem, A.R Palmer 2003. Biostratigraphy of China, Elsevie

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References

Prehistoric nautiloid genera {{paleo-Nautiloidea-stub