Plectronocerida

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m (Distribution: grammer)
m (Systematics and Evolution: spelling , Ectenolites)
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The Plectronocerida are divided into two families. These being the orthoconic and endogastric Plectronoceratidae and the exogastric Balkoceratidae. The Plectronoceratidae includes the earliest known definite cephalopod, Plectronoceras, along with six other named genera. The Balkoceratidae, based on Balkoceras, includes only two or three named genera.  
The Plectronocerida are divided into two families. These being the orthoconic and endogastric Plectronoceratidae and the exogastric Balkoceratidae. The Plectronoceratidae includes the earliest known definite cephalopod, Plectronoceras, along with six other named genera. The Balkoceratidae, based on Balkoceras, includes only two or three named genera.  
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The Plectronocerida gave rise to the Ellesmerocerida and the [[Protactinocerida]] in the early [[Trempealeauan]] and to the [[Yanhecerida]] in the early middle Trempealeauan. All became extinct before the end of the Cambrian, except for a few general (''Ectinolites'', and ''Clarkoceras'') that managed to squeak through into the Lower Ordovician [[Gasconadian]] stage.  
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The Plectronocerida gave rise to the Ellesmerocerida and the [[Protactinocerida]] in the early [[Trempealeauan]] and to the [[Yanhecerida]] in the early middle Trempealeauan. All became extinct before the end of the Cambrian, except for a few general (''Ectenolites'', and ''Clarkoceras'') that managed to squeak through into the Lower Ordovician [[Gasconadian]] stage.
===Distribution===
===Distribution===

Revision as of 13:12, 10 September 2008

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