ammonite(redirected from Ammonitida)
Also found in: Dictionary, Thesaurus, Medical.
ammonite(ăm`ənīt), one of a type of extinct marine cephalopodcephalopod
, member of the class Cephalopoda, the most highly organized group of mollusks (phylum Mollusca), and including the squids, octopuses, cuttlefish, and nautiluses. The class as a whole has become adapted for a free-swimming existence.
..... Click the link for more information. mollusk, related to the nautilusnautilus
or chambered nautilus,
cephalopod mollusk belonging to the sole surviving genus (Nautilus) of a subclass that flourished 200 million years ago, known as the nautiloids.
..... Click the link for more information. 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 MolluscaMollusca
, taxonomic name for the one of the largest phyla of invertebrate animals (Arthropoda is the largest) comprising more than 50,000 living mollusk species and about 35,000 fossil species dating back to the Cambrian period.
..... Click the link for more information. , class Cephalopoda, subclass Ammonoidea.
The Columbia Electronic Encyclopedia™ Copyright © 2013, Columbia University Press. Licensed from Columbia University Press. All rights reserved. www.cc.columbia.edu/cu/cup/
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