Mammal evolution: How ancient fossils are revealing the secrets of our earliest ancestors

 

A few years ago, I visited Liaoning Province in China, to study the region’s famous feather-covered dinosaur fossils. One day, after many hours of measuring bones and photographing feathers in a museum, I needed a break.

My Chinese colleagues exchanged a few hushed words of Mandarin and motioned for me to follow. “We have something secret to show you,” one of them said. “And it’s not a dinosaur.”

We left the museum, hopped into a car, and snaked through the narrow streets of Beipiao city, clogged with bicycles and noodle vendors. We pulled into an alleyway that opened into a small courtyard. Into a dark apartment we ventured, sidestepping a clutter of boxes and wooden crates.

One of my colleagues ducked into a side room and came out holding two rock slabs that fitted together like a jigsaw puzzle. On the surface was a brown smear, about the size of an apple

Mamals in the Era of Dinosaurs (Pictures)

 

Repenomamus mammals hunting for prey during the Mid-Jurassic Period of Europe. - Image ID: E1JM5E

Repenomamus

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Repenomamus

Repenomamus was the largest mammal of the Age of Dinosaurs. It was the first evidence of a Mesozoic mammal that was bigger than a mouse. In fact, Repenomamus was 3 feet long and weighed 26 to 31 pounds. This made it bigger than most of the dinosaurs of Liaoning, where it lived. In fact, there is even evidence that some dinos should have hidden from Repenomamus. In the stomach of Repenomamus were the bones of a baby Psittacosaurus. This is evidence that mammals were starting to get their revenge on dinsaurs by eating them. This would make Repenomamus the T-rex of Mesozoic mammals.