Merriam-Webster Collegiate Dictionary - ammonite

 noun  Etymology: Late Latin ~s, from Hebrew ‘Ammon Ammon (son of Lot), descendant of Ammon  Date: 1530 a member of a Semitic people who in Old Testament times lived east of the Jordan between the Jabbok and the Arnon  • ~ adjective AMMONITE  noun  Etymology: New Latin ~s, from Latin cornu Ammonis, literally, horn of Ammon  Date: 1758 any of a subclass (Ammonoidea) of extinct cephalopods especially abundant in the Mesozoic age that had flat spiral shells with the interior divided by septa into chambers  • ammonitic adjective