Hemiphragmoceratidae

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The Middle to Upper Silurian (possibly to Middle Devonian) Hemiphragmoceratidae were a very distinctive family of oncocerid cephalopods. At maturity, large lappets developed at the aperture of the body cavity, restricting the shell's opening. Exactly what sort of animal inhabited such a shell and how it lived are currently unknown.
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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: '''Hemiphragmoceratidae'''
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The Hemiphragmoceratidae is a rather distinctive family of [[Oncocerida|oncocerid]] cephalopods from the Middle and Upper [[Silurian]], possibly extending to the Middle [[Devonian]]. Derivation is probably from ''[[Oncoceras]]''. However phylogeny within the family is not yet worked out.
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Shells are compressed endogasric brevicones, curved adapically, straight adorally, with a ventral, nummuloidal, actinosiphonate siphuncle and an elaborately visored aperture. Actinosiphonate deposits continuous between segments. The mature peristome has a hyponomic sinus on spoutlike process, paired lateral sinuses and mid-dorsal salient.
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At maturity the shell's opening became restricted by large lappets that developed at the aperture of the body chamber. Exactly what sort of animal inhabited such a shell and how it lived remain unknown.
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'''Characters''' (from Sweet 1964): Compressed endogastric brevicones, curved adapically, straight adorally, with ventral, nummuloidal, actinosiphonate siphuncle and elaborately visored aperture. Actinosiphonate deposits continuous between segments. Mature peristome with hyponomic sinus on spoutlike process, paired lateral sinuses and mid-dorsal salient.
 
==Taxonomy==
==Taxonomy==
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[P68] Purnell, L. R. 1968. Catalog of the Type Specimens of Invertebrate Fossils. Part I: Paleozoic Cephalopoda. ''United States National Museum Bulletin'' 262: 1-198.
[P68] Purnell, L. R. 1968. Catalog of the Type Specimens of Invertebrate Fossils. Part I: Paleozoic Cephalopoda. ''United States National Museum Bulletin'' 262: 1-198.
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[S64] Sweet, W. C. 1964. Nautiloidea – Oncocerida. In ''Treatise on Invertebrate Paleontology'' pt. K. ''Mollusca 3. Cephalopoda – General Features – Endoceratoidea – Actinoceratoidea – Nautiloidea – Bactritoidea'' (R. C. Moore, ed.) pp. K277-K319. The Geological Society of America and the University of Kansas Press.
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[S64] Sweet, W. C. 1964. Nautiloidea – Oncocerida. In ''Treatise on Invertebrate Paleontology pt. K. Mollusca 3 pp. K277-K319''. Geological Society of America and the University of Kansas Press.
'''Credits'''
'''Credits'''
[[User:Christopher|Christopher]] 00:20, 16 January 2011 (UTC)
[[User:Christopher|Christopher]] 00:20, 16 January 2011 (UTC)
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[[User:John M|John]] 30 Sept 2014

Latest revision as of 13:57, 30 September 2014

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