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Nautiloidea
Nautiloidea (phylum Mollusca, class Cephalopoda) Subclass of cephalopods which possess a multichambered, external shell composed of calcium carbonate, which is siphunculate (see SIPHUNCLE) and may be coiled. The animal lives in the last-formed chamber, the body chamber. The gill structure is tetrabranchiate (four-gilled). Simple sutures are produced by contact between the internal septa and the shell wall. The subclass includes the oldest cephalopods, first recorded from Upper Cambrian rocks. They diversified and became common throughout the Palaeozoic, but were greatly reduced at the end of this era. Further diversification occurred in the Mesozoic, but the group dwindled again in the Cenozoic. There is only one extant genus, Nautilus, which dates from the Oligocene. See also PLECTRONOCERAS CAMBRIA.
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AILSA ALLABY and MICHAEL ALLABY. "Nautiloidea." A Dictionary of Earth Sciences. 1999. Encyclopedia.com. 28 May. 2012 <http://www.encyclopedia.com>. AILSA ALLABY and MICHAEL ALLABY. "Nautiloidea." A Dictionary of Earth Sciences. 1999. Encyclopedia.com. (May 28, 2012). http://www.encyclopedia.com/doc/1O13-Nautiloidea.html AILSA ALLABY and MICHAEL ALLABY. "Nautiloidea." A Dictionary of Earth Sciences. 1999. Retrieved May 28, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O13-Nautiloidea.html |
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Nautiloidea
Nautiloidea (phylum Mollusca, class Cephalopoda) A subclass of cephalopods which possess a multi-chambered, external shell composed of calcium carbonate, which is siphunculate (see SIPHUNCLE) and may be coiled. The gill structure is tetrabranchiate. Simple sutures are produced by contact between the internal septa and the shell wall. The subclass includes the oldest cephalopods, first recorded from Upper Cambrian rocks. They diversified and became common throughout the Palaeozoic but were greatly reduced at the end of this era. Further diversification occurred in the Mesozoic but the group dwindled again in the Cenozoic. There are more than 300 extinct genera and one extant genus, Nautilus, which dates from the Oligocene.
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Cite this article
MICHAEL ALLABY. "Nautiloidea." A Dictionary of Zoology. 1999. Encyclopedia.com. 28 May. 2012 <http://www.encyclopedia.com>. MICHAEL ALLABY. "Nautiloidea." A Dictionary of Zoology. 1999. Encyclopedia.com. (May 28, 2012). http://www.encyclopedia.com/doc/1O8-Nautiloidea.html MICHAEL ALLABY. "Nautiloidea." A Dictionary of Zoology. 1999. Retrieved May 28, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O8-Nautiloidea.html |
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