1 ene 1945 año - Many scientists think that finding the origin of cetaceans is to difficult

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"Because of their perfected adaptation to a completely aquatic life, with all its attendant conditions of respiration, circulation, dentition, locomotion, etc., the cetaceans are on the whole the most peculiar and aberrant of mammals. Their place in the sequence of cohorts and orders is open to question and is indeed quite impossible to determine in any purely objective way. "
Simpson (1945: p. 213) in his
Classification of Mammals

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