proostracum

noun

pro·​os·​tra·​cum

prōˈästrə̇kəm

plural proostraca

-kə

: the anterior horny or calcareous prolongation of the phragmocone of belemnites and related cephalopods

Word History

Etymology

New Latin, from pro- entry 1 + Greek ostrakon earthen vessel, potsherd, shell

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