Whales are a widely distributed and diverse group of fully aquatic placental marine mammals. They are an informal grouping within the infraorder Cetacea, which usually excludes dolphins and porpoises. Whales, dolphins and porpoises belong to the order Cetartiodactyla, which consists of even-toed ungulates. Their closest non-cetacean living relatives are the hippopotamuses, from which they and other cetaceans diverged about 54 million years ago.
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鲸鱼是一种广泛分布，多样化的完全水生胎盘海洋哺乳动物群体。它们是基于鲸目下的一个非正式分组，通常不包括海豚和鼠海豚。鲸鱼、海豚和鼠海豚属于偶蹄类目，包括偶蹄动物。它们最接近的非鲸类亲戚是河马，它们与其他鲸类分支大约在5400万年前。本文全面概述了鲸鱼及其演化的历史。



 

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目录
介绍
鲸鱼的历史
鲸鱼的种类
结论
参考文献