[via BBC NEWS | Science/Nature | 'Jurassic beaver' found in China]:

Castorocauda lutrasimilis, which was unearthed in China, is a species previously unknown to science.

It dates back to 164 million years ago, a time when mammals were thought to be primitive creatures confined to land.

But this animal was adapted to life in water, meaning scientists may now have to rethink their theories.

Who knew wet, furry and hot-blooded beavers roamed with dinosaurs. That goes to show that being a mammal and surviving the apocalyspe unleashed by a comet's crashing into Earth is really, really hot.