Plectronocerida

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Plectronocerids are found along with other coeval forms in late [[Franconian]] and Trempealeauan [[Fengshan Formation]] of Northern China and in the Trempealeauan San Saba Limestone of Central Texas. ''Plectronoceras'', the earliest known, is found in the Franconian and early Trempealeauan part of the Yenchou member of the Fengshan (Teichert 1988) . A specimen identified as a new species of ''Plectronoceras'' by Flower, 1964, ''Plectronoceras exile'', was found in the San Saba of Texas. Also from the San Saba is the narrow othoconic ''Palaeoceras'' sporting siphuncular bulbs in the juvenile portion and ''Balkoceras'', a slender, compressed, exogastric cyrtocone. Rare ''Plectronoceras'' is also found at Black Mountain in northwest Queensland, Aust.  
Plectronocerids are found along with other coeval forms in late [[Franconian]] and Trempealeauan [[Fengshan Formation]] of Northern China and in the Trempealeauan San Saba Limestone of Central Texas. ''Plectronoceras'', the earliest known, is found in the Franconian and early Trempealeauan part of the Yenchou member of the Fengshan (Teichert 1988) . A specimen identified as a new species of ''Plectronoceras'' by Flower, 1964, ''Plectronoceras exile'', was found in the San Saba of Texas. Also from the San Saba is the narrow othoconic ''Palaeoceras'' sporting siphuncular bulbs in the juvenile portion and ''Balkoceras'', a slender, compressed, exogastric cyrtocone. Rare ''Plectronoceras'' is also found at Black Mountain in northwest Queensland, Aust.  
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Of the remaining six genera from the Fengshan, listed in Teichert 1988, only two are found in the upper Yenchou/Lower Trempealeauan and in Wanwankou/Middle Trempealeauan. Both belong to the Plectronoceratidae. The remaining four are restricted to the Wanwankou. None are known to have survived the near end of the Cambrian extinction.  
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Of the remaining six genera from the Fengshan, listed in Teichert 1988, only two are found in the upper Yenchou/Lower Trempealeauan and in the Wanwankou/Middle Trempealeauan. Both belong to the Plectronoceratidae. The remaining four are restricted to the Wanwankou. None are known to have survived the near end of the Cambrian extinction.
===References===
===References===

Revision as of 13:10, 10 September 2008

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