Westonoceratidae

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(linked Lowoceratide)
(revised with added discussion)
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The Middle Ordovician to Middle Devonian westonoceratid lineage included the paraphyletic Westonoceratidae and its descendant families [[Lowoceratidae]] and Discosoridae.
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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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'''Characters''' (from Teichert 1964): Conchs mostly compressed exogastric cyrtocones (endogastric in Discosoridae, slender in Lowoceratidae); siphuncles moderate-sized; apertures constricted or open. Connecting rings thin to moderately thick; bullettes inflated in early forms, less so in adult Lowoceratidae and Discosoridae; parietal deposits in interior of siphuncle, forming endocones in later forms. Cameral deposits may be present.
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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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==Phylogeny/Taxonomy==
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''Teichertoceras'' apparently gave rise to two primary lineages within the Westonoceratdae. One consists of ''[[Westonoceras]]'' and ''[[Winnipegoceras'', (both m -u Ord), with ''[[Sinclairoceras]]'' and ''[[Simardocers]]'' mid Ord off shoots.  The  other consists of ''[[Faberoceras]]'' (m-u Ord), ''[[Clarkeswillia]]'' (u Ord), and  ''[[Glyptodentron]]'' (l Sil), with ''[[Reedsoceras]]'' (m Ord) and ''[[Hecatoceras]]'' (u Ord)  tentatively included.  ''Faberoceras'' is also the likely source of the Lowoceratdae.
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==Expanded phylogenic dendrogram==
  [[Discosorida|<==]]Westonoceratidae
  [[Discosorida|<==]]Westonoceratidae
     |  ''i. s.'': ''Broeggeroceras'' Sweet 1958 T64
     |  ''i. s.'': ''Broeggeroceras'' Sweet 1958 T64
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'''Credits'''
'''Credits'''
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[[User:Christopher|Christopher]] 23:14, 21 January 2011 (UTC)
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Christopher  21 January 2011
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[[user:John M|John]] 18 July 2014

Revision as of 23:06, 18 July 2014

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