Scientists have discovered the oldest mammalian ancestor in northeast China, according to a paper published in the latest issue of the journal Nature.
Named, Juramaia sinensis, or the Jurassic mother from China, the fossil of the small shrew-like animal was unearthed in China's northeast Liaoning Province, which has produced many amazing fossils in recent years.
Zhe-XI-Luo, a paleontologist at the Carnegie Museum of Natural History in Pittsburgh and his colleagues discovered the 160-million-year-old- fossil. Until this amazing find, the oldest ancestor to today's mammals was the dawn mother Eomaia- a 125-million year-old rat found in China.
Because it lived 160 million years ago, and nobody was there to sign the birth certificate of its descendants, Juramaia could be our great grandmother 160 million years removed or it could also be our great grand aunt that represents a relative on the side lines, lead author Zhe-Xi Luo told Discovery News.
The 160-million-year-old specimen has features that enabled scientists to place it among eutherians, or what is more commonly referred to as placental mammals. The creature was identified as a placental-eutherian, which is distinguished for having a placenta when pregnant (similar to humans and other modern mammals). This is in contrast to marsupials like kangaroos, which adopt a different reproductive strategy.
The new found fossil is well preserved with all its teeth intact. The skull is incomplete, but there are impressions of residual soft tissues, such as hair. It also retains its forepaw bones.
The teeth found on the fossil lead researchers to identify it as belonging to the eutherian lineage. The discovery pushes back the date when placental mammals and marsupial mammals took up their separate lines.
The Liaoning specimen is especially significant, because it means the fossil record now sits more comfortably with what genetic studies have been suggesting about the timing of the emergence of the different mammalian lineages, reports BBC.
Luo suspects the animal ate insects and was small and skinny and generally more active at night.
This new specimen is a real jewel among the spectacular treasure chest of the Chinese fossil record, said Gregory Wilson, an assistant professor at the University of Washington's Biology Department.
The exquisitely preserved anatomical details leave little doubt that we're looking at the earliest eutherian yet known, he continued, explaining that it was not quite a placental yet but on the line to placentals, he told Discovery News.