Westonoceratidae

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(revised with added discussion)
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The Westonoderatidae is a paraphyletic family of exogastric [[Discosorida|discosorids]] that lived from the middle and early Silurian, giving rise to the middle Silurian [[Lowoceratidae]]. Westonoceratid conchs (shells) are mostly compressed exogastric cyrocones - with the siphuncle on or near the outside curvature. Apertures may be constricted or open. Siphuncle are of moderate size, connecting rings thin to moderately thick. Bullettes, structures formed where siphuncle segments attach to the septal openings, are swolen and distinct.  Parietal deposits are common within siphuncles, forming endocones in advanced genera. Some have cameral deposits
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: Systematic Paleontology <br/>
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: Class: [[Cephalopods]] <br?>
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: Subclass: [[Nautiloidea]] <br/>
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: Order: [[Discosorida]] <br?>
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: '''Family: Westonoceratidae '''
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The Westonoceratidae is a paraphyletic family of exogastric [[Discosorida|discosorids]] that lived from the middle and early Silurian, giving rise to the middle Silurian [[Lowoceratidae]], ancestors of the [[Discosoridae]].
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==Description==
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Westonoceratid conchs (shells) are mostly compressed exogastric cyrocones - with the siphuncle on or near the outside curvature. Apertures may be constricted or open. Siphuncle are of moderate size, connecting rings thin to moderately thick. Bullettes, structures formed where siphuncle segments attach to the septal openings, are swolen and distinct.  Parietal deposits are common within siphuncles, forming endocones in advanced genera. Some have cameral deposits
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==Phylogeny==
The westonoceratidae were most likely derived from the [[Cyrtogomphoceratidae|cyrogomphoceratid]] ''[[Ulirichoceras]]'', during the middle Ordovician, through the ancestal ''[[Teichertoceras]]'', which retains the endogastric character of its ancestor in the early part of the phragmocone.  
The westonoceratidae were most likely derived from the [[Cyrtogomphoceratidae|cyrogomphoceratid]] ''[[Ulirichoceras]]'', during the middle Ordovician, through the ancestal ''[[Teichertoceras]]'', which retains the endogastric character of its ancestor in the early part of the phragmocone.  
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==Expanded phylogenic dendrogram==
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==Dendrogram==
  [[Discosorida|<==]]Westonoceratidae
  [[Discosorida|<==]]Westonoceratidae
     |  ''i. s.'': ''Broeggeroceras'' Sweet 1958 T64
     |  ''i. s.'': ''Broeggeroceras'' Sweet 1958 T64

Revision as of 23:46, 18 July 2014

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