The earliest known eutherian mammal

@article{Ji2002TheEK,
  title={The earliest known eutherian mammal},
  author={Qiang Ji and Zhe‐Xi Luo and Chong-xi Yuan and John R. Wible and Jian-Ping Zhang and Justin A. Georgi},
  journal={Nature},
  year={2002},
  volume={416},
  pages={816-822}
}
The skeleton of a eutherian (placental) mammal has been discovered from the Lower Cretaceous Yixian Formation of northeastern China. We estimate its age to be about 125 million years (Myr), extending the date of the oldest eutherian records with skull and skeleton by about 40–50 Myr. Our analyses place the new fossil at the root of the eutherian tree and among the four other known Early Cretaceous eutherians, and suggest an earlier and greater diversification of stem eutherians that occurred… 

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