Troedssonellidae

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The Troedssonellidae were a Lower to Middle Ordovician family of orthocerid cephalopods that formed endocones in the apical part of their siphuncles.
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The '''Troedssonellidae''' is a family of Ordovician [[Michelinoceratida|michelinocerids]], (=Orthocerida s.s.) established by Kodayashi, 1935, characterized by essentially tubular siphuncle segments with short straight septal necks and thin homogenous connecting rings;  the siphuncle containing a lining that thickens adapically into very slender endocones
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The Troedssonellidae has its origin in the [[Michelinoceratidae]] in Cassinian stage near the end of the Early Ordovician, the earliest known being ''Tajaoceras'', which gave rise to ''Buttsoceras''.  Also included are ''Troedssonella'' and ''Ctenoceras''.
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The Troedssonellidae extend into the Whiterock stage at be beginning of the Middle Ordovician and give rise to the  [[Striatoceratidae]] of the upper Whiterockian and Chazyan stages,(lower Middle Ordovician), which  have expanded siphuncle segments, and either directly or through the Striatoceratidae to the large Upper Ordovician [[Narthecoceratidae]].
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'''Characters''' (from Sweet 1964): Siphuncle suborthochoanitic; continual endosiphuncular lining of parietal deposits prolonged adapically to form endocones.
 
==References==
==References==
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[S64] Sweet, W. C. 1964. Nautiloidea – Orthocerida. In ''Treatise on Invertebrate Paleontology'' pt. K. ''Mollusca 3. Cephalopoda – General Features – Endoceratoidea – Actinoceratoidea – Nautiloidea – Bactritoidea'' (R. C. Moore, ed.) pp. K216-K261. The Geological Society of America and the University of Kansas Press.
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Flower, R. H. 1976  Ordovician Cephalopod Faunas and Their Role in Correlation. The Ordovician System: Proceedings of a Palaeontological Society Symposium.
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Flower, R. H. r 1963 Notes on the Michellinoceratida.  Mem 9, New Mexico Institute of Mineral Technology. Socorro, NM
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Hook, Stephen C. & Rousseau H Flower 1976. ''Tajaroceras'' and the origin of the Troedssonellidae. Jour of Paleontology v. 50 no 2. p 293 -300. March 1976.
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Sweet, W. C. 1964. Nautiloidea – Orthocerida. In ''Treatise on Invertebrate Paleontology'' pt. K. ''Mollusca 3''. Geological Society of America and University of Kansas Press.
'''Credits'''
'''Credits'''
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[[User:Christopher|Christopher]] 21:51, 27 January 2011 (UTC)
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[[User:Christopher|Christopher]] 27 January 2011 <br/>
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[[user:John M|John]] 21 July 2014

Latest revision as of 23:46, 21 July 2014

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