Valcouroceratidae

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m (Protected "Valcouroceratidae" ([move=sysop] (indefinite)))
(Taxonomy: added discussion)
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==Taxonomy==
==Taxonomy==
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Eight genera are known, all from the middle and/or upper Ordovician of North America, differing as to the degree of curvature, amount of expansion, cross section, and specifics of the actinosiphonate siphuncle linings; here shown.
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  [[Oncocerida|<==]]Valcouroceratidae
  [[Oncocerida|<==]]Valcouroceratidae
     |--''Actinomorpha'' Flower 1943 S64
     |--''Actinomorpha'' Flower 1943 S64
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         `--''F. canyonense'' Foerste 1935 P68
         `--''F. canyonense'' Foerste 1935 P68
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<nowiki>*</nowiki> Type species of generic name indicated
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<nowiki>*</nowiki> indicates type species.
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''Valcouroceras'', the type genus, named by Rousseau Flower, 1943, for Valcour Island on Lake Champlain, where first found, has the strongest curviture (exogastric), and greatest rate of expansion of any of these.  ''Manitoulinoceras'' named by Foeste,1924, is perhaps the most opposite in that it has the slowest rate of expansion of the eight. ''Kindleoceras'' is similar but has a triangular cross section. That of ''Manitoulinoceras'' is subcircular. ''Augustoceras'', ''Fayettoceras'', ''Minganoceras'', and ''Staufferoceras'' are intermediate, with moderately curved exogastric cyrtocones.
==References==
==References==

Revision as of 02:08, 22 November 2012

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