漸ぜん新しん世せいぜんしんせいMeanings1nounOligocene epochGeological epoch from about 33.9 to 23 million years ago, between the Eocene and Miocene.漸ぜん新しん世せいは哺ほ乳にゅう類るいの多た様よう化かが進すすんだ時じ代だいで