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Fossil dates mammal evolution

PITTSBURGH, Aug. 24 (UPI) -- Paleontologists say a 160-million-year-old fossil found in China provides insights into the earliest ancestors of most of today's mammal species.

Scientists led by Carnegie Museum of Natural History paleontologist Zhe-Xi Luo said Juramaia sinensis, a small shrew-like mammal that lived in China during the Jurassic period, is the earliest known fossil of eutherians, the group that evolved to include all mammals that provide nourishment to unborn young via a placenta.

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Researchers say the newly found fossil suggests the date when eutherian mammals diverged from other mammals occurred 35 million years earlier than previously thought, a Carnegie release reported Wednesday.

The fossil of Juramaia sinensis was discovered in the Liaoning province in northeast China; the name means "Jurassic mother from China."

"Understanding the beginning point of placentals is a crucial issue in the study of all mammalian evolution," Luo says.

The date of an evolutionary divergence, when an ancestor species splits into two descendant lineages, is among the most important pieces of information an evolutionary scientist can have, he said.

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