Trimeroceratidae

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The Middle Silurian Trimeroceratidae resembled the related Hemiphragmoceratidae in having the shell aperture visored by encroaching lappets. The two families mainly differed in the structure of the siphuncle, that of Trimeroceratidae being slender and without actinosiphonate deposits.
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<u>Systematic Paleontology</u> <br/>
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Class: [[Cephalopoda]]  <br/>
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Subclass: [[Nautiloidea]]  <br/>
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Order: [[Oncocerida]]  <br/>
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Family: Trimeroceratide
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The Trimeroceratidae is a family of Middle [[Silurian]] [[Oncocerida|oncocerids]] characerized in general by compressed exogastric breviconas with a slender, empty siphucle, visored aperture, and a mature peristome with a median dorsal sinus.
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Trimeroceratidae superficially resemble the [[Hemiphragmoceratidae]] but instead have slender siphuncles without actinosiphonate deposits and shell curved exogastrically upward contrasting with the downward endogastric curvature characterisitc of the Hemiphramoceratidae
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'''Characters''' (from Sweet 1964): Exogastric, mostly compressed brevicones with slender, empty siphuncles. Aperture visored; mature peristome with median dorsal sinus.
 
==References==
==References==
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[T64] Teichert, C. 1964. Morphology of hard parts. In ''Treatise on Invertebrate Paleontology'' pt. K. ''Mollusca 3. Cephalopoda – General Features – Endoceratoidea – Actinoceratoidea – Nautiloidea – Bactritoidea'' (R. C. Moore, ed.) pp. K13-K53. The Geological Society of America and the University of Kansas Press.
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Walter C. Sweet, 1964. Nautiloidea- Oncocerida. Treatise on Invertebrate Paleontology, Part K, Mollsca 3. Geological Society of America and University of Kansas Press.  
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'''Credits'''
'''Credits'''
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[[User:Christopher|Christopher]] 00:23, 16 January 2011 (UTC)
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[[User:Christopher|Christopher]] 16 January 2011 <br/>
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[[User: John M|John M]]  30 Sept 2014

Latest revision as of 14:37, 30 September 2014

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