ammonite(redirected from Ammonitida)
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ammonite (ămˈənīt), one of a type of extinct marine cephalopod mollusk, related to the nautilus and resembling it in having an elaborately coiled and chambered shell. Unlike the interiors of nautilus shells, the chambers of ammonite shells display intricately shaped septa and sutures. The type included numerous species, which were widely distributed during the Mesozoic era, about 200 million years ago. Ammonites are classified in the phylum Mollusca, class Cephalopoda, subclass Ammonoidea.
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An explosive containing 70-95% ammonium nitrate.
A fossil shell of the cephalopod order Ammonoidea.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
1. any extinct marine cephalopod mollusc of the order Ammonoidea, which were common in Mesozoic times and generally had a coiled partitioned shell. Their closest modern relative is the pearly nautilus
2. the shell of any of these animals, commonly occurring as a fossil
1. an explosive consisting mainly of ammonium nitrate with smaller amounts of other substances, such as TNT
2. a nitrogenous fertilizer made from animal wastes
Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005