Definition of rudist in English:

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Pronunciation: /ˈruːdɪst/
(also rudistid /ruːˈdɪstɪd/)


A cone-shaped fossil bivalve mollusc which formed colonies resembling reefs in the Cretaceous period.
Example sentences
  • An extinct group of Mesozoic bivalves, the rudistids, became closely adapted to a cemented mode of life: one valve became conical while the other formed a lid.
  • Cretaceous radiations of rudists were apparently initiated during periods of globally high sea level and the Lebanon decapod faunas are a part of this general increasing invertebrate diversity.
  • This member contains abundant and diverse mid-Cretaceous shallow-marine invertebrates, including reef corals and rudist bivalves.


Late 19th century: from modern Latin Rudista (former group name), from Latin rudis 'rude'; for the variant spelling see -id3.

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