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Thursday, August 25, 2011

160-million-year-old fossil redefines mammal history

A small, 160-million-year-old Chinese fossil has something big to say about the emergence of mammals on Earth.

The shrew-like creature is the earliest known example of an animal that used a placenta to provide nourishment to their unborn young.

Its features clearly set it apart from marsupial mammals, which adopt a very different reproductive strategy.

The discovery pushes back the date the two groups took up their separate lines, according to Nature magazine.

The journal carries a paper written by a team of palaeontologists led by Zhe-Xi Luo from the Carnegie Museum of Natural History, Pittsburgh, US.

It describes the fossil remains of an animal unearthed in China's northeast Liaoning Province, which has produced so many stunning fossils in recent years.

The new specimen, which the scientists call Juramaia sinensis, records many of the key features of the long-dead organism, including its skull and even impressions of soft tissues such as hair.

But, most importantly, the Juramaia fossil also retains a full set of teeth and forepaw bones. more