Juramaia sinensis

This is Juramaia sinensis, the oldest known eutherian (placental) mammal, discovered in China and published last year. This shrew-like animal lived around 160 million years ago, 25 million years earlier than the previous record holder. Paleontologists were pleased with this discovery because DNA studies and comparisons of bones and teeth made them think that the split between placental mammals and marsupials ought to have happened earlier than their oldest eutherian fossils. And it did.