Placental mammal: 160 million years
About 90 per cent of today's mammals — including us — are placental mammals. We give birth to fully developed offspring that have been nurtured in the womb.
The earliest evidence we have of this group scurried across the forest floor of what is now China, 160 million years ago.
In 2011, Chinese scientists discovered the fossil remains of a small mousey or shrew-like animal, which they named Juramala sinesis.
Two years after its discovery, another equally old fossil of a rat-like mammal Rugosodon eurasiaticus was discovered — also in China.
These bump the previous title holder for oldest-known placental mammal — again, from China — a squirrel-like animal dating from 125 million years ago.
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