An Early Cretaceous Tribosphenic Mammal and Metatherian Evolution

@article{Luo2003AnEC,
  title={An Early Cretaceous Tribosphenic Mammal and Metatherian Evolution},
  author={Zhe‐Xi Luo and Qiang Ji and John R. Wible and Chong-xi Yuan},
  journal={Science},
  year={2003},
  volume={302},
  pages={1934 - 1940}
}
Derived features of a new boreosphenidan mammal from the Lower Cretaceous Yixian Formation of China suggest that it has a closer relationship to metatherians (including extant marsupials) than to eutherians (including extant placentals). This fossil dates to 125 million years ago and extends the record of marsupial relatives with skeletal remains by 50 million years. It also has many foot structures known only from climbing and tree-living extant mammals, suggesting that early crown therians… 

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