Fossil-hunters in China have discovered two skeletons from a kind of animal never seen before: a dog-sized mammal that lived about 135 million years ago. The discovery overturns the conventional wisdom that the earliest mammals were all rodent-sized and meek. As NPR's Christopher Joyce reports, this animal apparently munched on dinosaurs.

Nestled inside one of the skeletons -- where its stomach once was -- scientists found a tiny set of bones, the remains of a small dinosaur about five inches long from tip to tail. Scientists say the find will trigger some rethinking about the relationship between mammals and dinosaurs, and how they influenced each other.

The fossils, called Repenomamus, were found in China's Liaoning Province, a region that's produced numerous unique fossils in recent years. The findings appear in the current issue of the journal Nature.

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