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Nature 409, 28-31 (4 January 2001) | doi:10.1038/35051199

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Mammalian evolution: Relationships to chew over

Anne Weil

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Did advanced mammals evolve on the southern continents and then move north? Not according to a new study, which concludes that such mammals evolved in both the south and the north.

There are three groups of living mammals — placentals, marsupials and the monotremes. The first two, along with some mammalian fossil relatives, have so-called 'tribosphenic' teeth, which provide a highly efficient way of chopping and grinding food.