Cretaceous eutherians and Laurasian origin for placental mammals near the K/T boundary

@article{Wible2007CretaceousEA,
  title={Cretaceous eutherians and Laurasian origin for placental mammals near the K/T boundary},
  author={John R. Wible and Guillermo W. Rougier and Michael J. Novacek and Robert J. Asher},
  journal={Nature},
  year={2007},
  volume={447},
  pages={1003-1006}
}
Estimates of the time of origin for placental mammals from DNA studies span nearly the duration of the Cretaceous period (145 to 65 million years ago), with a maximum of 129 million years ago and a minimum of 78 million years ago. Palaeontologists too are divided on the timing. Some support a deep Cretaceous origin by allying certain middle Cretaceous fossils (97–90 million years old) from Uzbekistan with modern placental lineages, whereas others support the origin of crown group Placentalia… 

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