A small, 160-million-year-old Chinese fossil has provided scientists with more information on the emergence of mammals on Earth.
Named Juramaia sinensis, which means the "Jurassic mother from China," the small, shrew-like animal used to mainly live in trees in contrast to dinosaurs who occupied most of the land space.
The study was led by a team of scientists including Luo, a Carnegie Museum of Natural History palaeontologist, and his colleagues Chong-Xi Yuan, Qing-Jin Meng and Qiang Ji .
"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," says Zhe-Xi Luo, lead author of a paper appearing in the journal Nature.
The fossils include an incomplete skull, part of the skeleton and impressions of residual soft tissues such as hair and even a set of teeth but the reports reveal its features set it apart from marsupial mammals, which have a different reproductive strategy.
"The teeth of Juramaia show all the typical eutherian dental features," Dr Luo the BBC quoted Luo as saying.
"Specifically, eutherians have three molars, and five premolars. This is in contrast to metatherians characterized by four molars and three premolars.
"Details aside, the difference in teeth of Juramaia allow us to identify it as belonging to the eutherian lineage. In addition, the forelimb and wrist bones show some eutherian features; they completely lack the important diagnostic features of metatherians-marsupials."
According to the study, the shrew-like creature represent the earliest known case of an animal that used a placenta to provide nourishment to their unborn young through the umbilical cord.
"Marsupials, by contrast, make up for the short development of foetuses in the mother by having a longer pouch life before the foetuses become independent," says Luo. "Marsupials just optioned for a different reproductive strategy."
The document also says the animal's hand structure suggests that it was a capable climber
"So I imagine this animal to be a shew-sized insectivorous mammal that hunted insects and was capable of being active in the trees." Luo said.