A newly found mammal fossil pushes back the date when two lines of mammals diverged, researchers say. Scientists unearthed the 160-million-year-old fossil of a shrew-like mammal in northeast China.
Named the "Jurassic mother from China" (Juramaia sinensis), the newfound fossil species is the earliest known ancestor of placental mammals—animals, such as humans, that give birth to relatively mature, live young—according to a new study.
The small, furry placental mammal lived in what is now north east China during the Jurassic era when dinosaurs ruled the Earth.
Features of the creature 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.
Until now, the oldest known ancestor to placentals was a small mammal that dates back about 125 million years, to the Cretaceous period.
The new fossil has a well-preserved skull with all its teeth intact. Based on the teeth, the researchers determined that the mammal was more closely related to modern placentals than to modern marsupials.
"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.
Luo, a Carnegie Museum of Natural History paleontologist, and his colleagues Chong-Xi Yuan, Qing-Jin Meng and Qiang Ji analyzed the well-preserved remains of the prehistoric animal, which was discovered in Liaoning Province.
The small, furry placental mammal lived in what is now north east China during the Jurassic era when dinosaurs ruled the Earth.
Features of the creature 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.
Until now, the oldest known ancestor to placentals was a small mammal that dates back about 125 million years, to the Cretaceous period.
The new fossil has a well-preserved skull with all its teeth intact. Based on the teeth, the researchers determined that the mammal was more closely related to modern placentals than to modern marsupials.
"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.
Luo, a Carnegie Museum of Natural History paleontologist, and his colleagues Chong-Xi Yuan, Qing-Jin Meng and Qiang Ji analyzed the well-preserved remains of the prehistoric animal, which was discovered in Liaoning Province.
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