Thewissen J G, Hussain S T
Department of Biological Anthropology and Anatomy, Duke University Medical School, Durham, North Carolina 27710.
Nature. 1993 Feb 4;361(6411):444-5. doi: 10.1038/361444a0.
All described fossil and Recent cetaceans have relatively similar ear bones (malleus, incus and stapes) that strongly diverge from those of land mammals. Here we report that the hearing organ of the oldest whale, Pakicetus, is the only known intermediate between that of land mammals and aquatic cetaceans (whales, dolphins and porpoises). The incus of Pakicetus is intermediate with respect to inflation, crural proportions, and position of the mallear joint. The incus and mandible of Pakicetus indicate that the path of soundwaves to its ear resembled that of land mammals. These fossils suggest that the first whale was amphibious, and corroborate the hypothesis that artiodactyls (for example, pigs, camels and ruminants) are the closest extant relatives of cetaceans.
所有已描述的化石鲸类和现代鲸类都有相对相似的耳骨（锤骨、砧骨和镫骨），这些耳骨与陆地哺乳动物的耳骨有很大差异。在此我们报告，最古老的鲸鱼——巴基鲸的听觉器官是已知的陆地哺乳动物和水生鲸类（鲸鱼、海豚和鼠海豚）之间的唯一中间形态。巴基鲸的砧骨在充气情况、腿部比例以及锤骨关节位置方面处于中间状态。巴基鲸的砧骨和下颌骨表明，声波传入其耳朵的路径与陆地哺乳动物相似。这些化石表明，最早的鲸鱼是两栖动物，证实了偶蹄目动物（例如猪、骆驼和反刍动物）是鲸类现存最近亲属的假说。
