ammonite

ammonite

(ăm′ə-nīt′)

n.

1. An extinct cephalopod mollusk of the order Ammonitida of the Permian to Cretaceous Periods, having a thick, usually coiled shell characterized by intricate suture patterns where the septa between individual chambers join the outer shell wall.

2. An ammonoid.

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am′mo·nit′ic (-nĭt′ĭk) adj.

The American Heritage® Medical Dictionary Copyright © 2007, 2004 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved.

ammonite

a name given to a large group of fossil cephalopod molluscs of late Palaeozoic and Mesozoic time that possessed a spiral shell very similar to that of Nautilus.

Collins Dictionary of Biology, 3rd ed. © W. G. Hale, V. A. Saunders, J. P. Margham 2005