PAUL D STEWART / SCIENCE PHOTO LIBRARY PAUL D STEWART / SCIENCE PHOTO LIBRARY
Woodcut by Gesner "Icones Animalium" publ. Christof Froschover, Zurich, 1560. Gesner, followed Rondelet and Belon in grouping marine mammals with fish based on habitat. But he (and Rondelet) saw that unlike fishes with scales the dolphins have hearts with two divided chambers and foetus were in a placenta like land viviparous quadrupeds. They also fed their young milk as seen here. He considered marine mammals to be a type of aquatic quadruped. But in an age before clear taxonomy, it was by their life in the water that he chose to define them. The realisation that cetaceans were seperate from the fishes and should be grouped with the viviparous qudrapeds had to wait two centuries for Linnaeus, 1758. He coined the term cetacea and put them with the mammals based on breathing by lungs, hollow ears, internal fertilization, and production of milk.
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