然而，专家认为巴基鲸是已经灭绝的食肉哺乳动物中爪类和鲸类之间的过渡物种。
Other features, however, show experts that Pakicetus is a transitional form between a group of extinct flesh-eating mammals, the mesonychids, and cetaceans.
“巴基鲸”化石由一个原细胞的完整头盖骨所组成，这是现代鲸类祖先中已经灭绝的一个物种。
The fossil consists of a complete skull of an archaeocyte, an extinct group of ancestors of modern cetaceans.
在南极地区，由于海洋温度的上升和海冰的融化，露脊鲸主要的食物来源南极磷虾受到了严重威胁，这反过来也危及到了鲸类的生存。
Krill, the whales' main source of food, are threatened by higher ocean temperatures and melting sea ice around the Antarctic, which would in turn hurt the whales' chances of survival.
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