From Land to Water: the Origin of Whales, Dolphins, and Porpoises

@article{Thewissen2009FromLT,
  title={From Land to Water: the Origin of Whales, Dolphins, and Porpoises},
  author={J. G. M. Thewissen and Lisa Noelle Cooper and John C. George and Sunil Bajpai},
  journal={Evolution: Education and Outreach},
  year={2009},
  volume={2},
  pages={272-288}
}
Cetaceans (whales, dolphins, and porpoises) are an order of mammals that originated about 50 million years ago in the Eocene epoch. Even though all modern cetaceans are obligate aquatic mammals, early cetaceans were amphibious, and their ancestors were terrestrial artiodactyls, similar to small deer. The transition from land to water is documented by a series of intermediate fossils, many of which are known from India and Pakistan. We review raoellid artiodactyls, as well as the earliest… 

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Protocetid cetaceans (Mammalia) from the Eocene of India

Two new genera and species are described: Kharodacetus sahnii and Dhedacetus hyaeni, both of which are protocetid cetaceans from District Kutch in the State of Gujarat and were recovered in deposits approximately 42 million years old.
...

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